diff --git a/src/main/java/org/kkumulkkum/server/controller/PromiseController.java b/src/main/java/org/kkumulkkum/server/controller/PromiseController.java
index c0be657..b35f285 100644
--- a/src/main/java/org/kkumulkkum/server/controller/PromiseController.java
+++ b/src/main/java/org/kkumulkkum/server/controller/PromiseController.java
@@ -3,6 +3,7 @@
 import jakarta.validation.Valid;
 import lombok.RequiredArgsConstructor;
 import org.kkumulkkum.server.annotation.IsMember;
+import org.kkumulkkum.server.annotation.IsParticipant;
 import org.kkumulkkum.server.annotation.UserId;
 import org.kkumulkkum.server.dto.promise.PromiseCreateDto;
 import org.kkumulkkum.server.dto.promise.response.PromiseDto;
@@ -31,12 +32,12 @@ public ResponseEntity<Void> createPromise(
         return ResponseEntity.created(URI.create(promiseId.toString())).build();
     }
 
+    @IsParticipant(promiseIdParamIndex = 0)
     @PatchMapping("/promises/{promiseId}/completion")
     public ResponseEntity<Void> completePromise(
-            @UserId Long userId,
             @PathVariable Long promiseId
     ) {
-        promiseService.completePromise(userId, promiseId);
+        promiseService.completePromise(promiseId);
         return ResponseEntity.ok().build();
     }
 
diff --git a/src/main/java/org/kkumulkkum/server/domain/UserInfo.java b/src/main/java/org/kkumulkkum/server/domain/UserInfo.java
index da25c5c..26e32b7 100644
--- a/src/main/java/org/kkumulkkum/server/domain/UserInfo.java
+++ b/src/main/java/org/kkumulkkum/server/domain/UserInfo.java
@@ -59,4 +59,27 @@ public void deleteImage() {
     public void updateName(String name) {
         this.name = name;
     }
+
+    public void addPromiseCount() {
+        this.promiseCount++;
+    }
+
+    public void addLateCount() {
+        this.tardyCount++;
+    }
+
+    public void addLateTime(long time) {
+        this.tardySum += time;
+    }
+
+    public void levelUp() {
+        int count = this.promiseCount - this.tardyCount;
+        if (count == 2) {
+            this.level = 2;
+        } else if (count == 5) {
+            this.level = 3;
+        } else if (count == 10) {
+            this.level = 4;
+        }
+    }
 }
diff --git a/src/main/java/org/kkumulkkum/server/dto/user/response/UserDto.java b/src/main/java/org/kkumulkkum/server/dto/user/response/UserDto.java
index a109d13..10f5f34 100644
--- a/src/main/java/org/kkumulkkum/server/dto/user/response/UserDto.java
+++ b/src/main/java/org/kkumulkkum/server/dto/user/response/UserDto.java
@@ -16,7 +16,7 @@ public static UserDto from(UserInfo userInfo) {
                 userInfo.getLevel(),
                 userInfo.getPromiseCount(),
                 userInfo.getTardyCount(),
-                userInfo.getTardySum(),
+                userInfo.getTardySum()/60,
                 userInfo.getProfileImg()
         );
     }
diff --git a/src/main/java/org/kkumulkkum/server/exception/code/PromiseErrorCode.java b/src/main/java/org/kkumulkkum/server/exception/code/PromiseErrorCode.java
index 2f56ce0..5c407d2 100644
--- a/src/main/java/org/kkumulkkum/server/exception/code/PromiseErrorCode.java
+++ b/src/main/java/org/kkumulkkum/server/exception/code/PromiseErrorCode.java
@@ -6,8 +6,11 @@
 
 @Getter
 @AllArgsConstructor
-public enum PromiseErrorCode {
-    //404 Not Found
+public enum PromiseErrorCode implements DefaultErrorCode {
+    // 400 Bad Request
+    NOT_PAST_DUE(HttpStatus.BAD_REQUEST, 40010, "약속 시간이 지나지 않았습니다."),
+    NOT_ARRIVED_PARTICIPANT_EXISTS(HttpStatus.BAD_REQUEST, 40020, "도착하지 않은 참여자가 있습니다."),
+    // 404 Not Found
     NOT_FOUND_PROMISE(HttpStatus.NOT_FOUND, 40430, "약속을 찾을 수 없습니다."),
     ;
 
diff --git a/src/main/java/org/kkumulkkum/server/repository/ParticipantRepository.java b/src/main/java/org/kkumulkkum/server/repository/ParticipantRepository.java
index 814fb79..a7d0e01 100644
--- a/src/main/java/org/kkumulkkum/server/repository/ParticipantRepository.java
+++ b/src/main/java/org/kkumulkkum/server/repository/ParticipantRepository.java
@@ -22,7 +22,7 @@ public interface ParticipantRepository extends JpaRepository<Participant, Long>
             "JOIN Member m ON p.member.id = m.id " +
             "JOIN UserInfo ui ON m.user.id = ui.user.id " +
             "WHERE p.promise.id = :promiseId")
-    List<ParticipantStatusUserInfoDto> findAllByPromiseId(Long promiseId);
+    List<ParticipantStatusUserInfoDto> findAllByPromiseIdWithUserInfo(Long promiseId);
 
     @Query("SELECT new org.kkumulkkum.server.dto.participant.response.LateComerDto " +
             "(p.id, ui.name, ui.profileImg) " +
@@ -42,4 +42,6 @@ public interface ParticipantRepository extends JpaRepository<Participant, Long>
             ") THEN TRUE ELSE FALSE END " +
             "FROM Participant p")
     boolean existsByPromiseIdAndUserId(Long promiseId, Long userId);
+
+    List<Participant> findAllByPromiseId(Long promiseId);
 }
diff --git a/src/main/java/org/kkumulkkum/server/repository/PromiseRepository.java b/src/main/java/org/kkumulkkum/server/repository/PromiseRepository.java
index 8ec5b4a..b05ec44 100644
--- a/src/main/java/org/kkumulkkum/server/repository/PromiseRepository.java
+++ b/src/main/java/org/kkumulkkum/server/repository/PromiseRepository.java
@@ -2,10 +2,16 @@
 
 import org.kkumulkkum.server.domain.Promise;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
 
 import java.util.List;
 
 public interface PromiseRepository extends JpaRepository<Promise, Long> {
 
     List<Promise> findAllByMeetingId(Long meetingId);
+
+    @Query("SELECT CASE WHEN EXISTS " +
+            "(SELECT p FROM Participant p WHERE p.promise.id = :promiseId AND p.arrivalAt IS NULL) " +
+            "THEN TRUE ELSE FALSE END FROM Participant p")
+    boolean existsByArrivedAtIsNull(Long promiseId);
 }
diff --git a/src/main/java/org/kkumulkkum/server/repository/UserInfoRepository.java b/src/main/java/org/kkumulkkum/server/repository/UserInfoRepository.java
index 19d308d..3a0d82f 100644
--- a/src/main/java/org/kkumulkkum/server/repository/UserInfoRepository.java
+++ b/src/main/java/org/kkumulkkum/server/repository/UserInfoRepository.java
@@ -2,10 +2,16 @@
 
 import org.kkumulkkum.server.domain.UserInfo;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
 
 import java.util.Optional;
 
 public interface UserInfoRepository extends JpaRepository<UserInfo, Long> {
 
     Optional<UserInfo> findByUserId(Long id);
+
+    @Query("SELECT ui FROM UserInfo ui " +
+            "JOIN Participant p ON ui.user.id = p.member.user.id " +
+            "WHERE p.id = :id")
+    Optional<UserInfo> findByParticipantId(Long id);
 }
diff --git a/src/main/java/org/kkumulkkum/server/service/participant/ParticipantRetriever.java b/src/main/java/org/kkumulkkum/server/service/participant/ParticipantRetriever.java
index 28da87d..defc504 100644
--- a/src/main/java/org/kkumulkkum/server/service/participant/ParticipantRetriever.java
+++ b/src/main/java/org/kkumulkkum/server/service/participant/ParticipantRetriever.java
@@ -22,10 +22,14 @@ public Participant findByPromiseIdAndUserId(Long promiseId, Long userId) {
                 .orElseThrow(() -> new ParticipantException(ParticipantErrorCode.NOT_JOINED_PROMISE));
     }
 
-    public List<ParticipantStatusUserInfoDto> findAllByPromiseId(Long promiseId) {
+    public List<Participant> findAllByPromiseId(Long promiseId) {
         return participantRepository.findAllByPromiseId(promiseId);
     }
 
+    public List<ParticipantStatusUserInfoDto> findAllByPromiseIdWithUserInfo(Long promiseId) {
+        return participantRepository.findAllByPromiseIdWithUserInfo(promiseId);
+    }
+
     public List<LateComerDto> findAllLateComersByPromiseId(Long promiseId) {
         return participantRepository.findAllLateComersByPromiseId(promiseId);
     }
diff --git a/src/main/java/org/kkumulkkum/server/service/participant/ParticipantService.java b/src/main/java/org/kkumulkkum/server/service/participant/ParticipantService.java
index b323b36..04abbf2 100644
--- a/src/main/java/org/kkumulkkum/server/service/participant/ParticipantService.java
+++ b/src/main/java/org/kkumulkkum/server/service/participant/ParticipantService.java
@@ -62,7 +62,7 @@ public PreparationStatusDto getPreparation(final Long userId, final Long promise
 
     @Transactional(readOnly = true)
     public ParticipantsDto getParticipants(final Long promiseId) {
-        List<ParticipantStatusUserInfoDto> participants = participantRetriever.findAllByPromiseId(promiseId);
+        List<ParticipantStatusUserInfoDto> participants = participantRetriever.findAllByPromiseIdWithUserInfo(promiseId);
         return ParticipantsDto.from(
                 participants.stream()
                         .map(this::createParticipantDto)
diff --git a/src/main/java/org/kkumulkkum/server/service/promise/PromiseRetriever.java b/src/main/java/org/kkumulkkum/server/service/promise/PromiseRetriever.java
index ec9ae7c..4ebd98c 100644
--- a/src/main/java/org/kkumulkkum/server/service/promise/PromiseRetriever.java
+++ b/src/main/java/org/kkumulkkum/server/service/promise/PromiseRetriever.java
@@ -23,4 +23,8 @@ public Promise findById(Long id) {
         return promiseRepository.findById(id)
                 .orElseThrow(() -> new PromiseException(PromiseErrorCode.NOT_FOUND_PROMISE));
     }
+
+    public boolean existsByArrivedAtIsNull(Long promiseId) {
+        return promiseRepository.existsByArrivedAtIsNull(promiseId);
+    }
 }
diff --git a/src/main/java/org/kkumulkkum/server/service/promise/PromiseService.java b/src/main/java/org/kkumulkkum/server/service/promise/PromiseService.java
index 84cea51..dc4e494 100644
--- a/src/main/java/org/kkumulkkum/server/service/promise/PromiseService.java
+++ b/src/main/java/org/kkumulkkum/server/service/promise/PromiseService.java
@@ -2,18 +2,20 @@
 
 import jakarta.persistence.EntityManager;
 import lombok.RequiredArgsConstructor;
-import org.kkumulkkum.server.domain.Meeting;
-import org.kkumulkkum.server.domain.Member;
-import org.kkumulkkum.server.domain.Participant;
-import org.kkumulkkum.server.domain.Promise;
+import org.kkumulkkum.server.domain.*;
 import org.kkumulkkum.server.dto.promise.PromiseCreateDto;
 import org.kkumulkkum.server.dto.promise.response.PromiseDto;
 import org.kkumulkkum.server.dto.promise.response.PromisesDto;
+import org.kkumulkkum.server.exception.PromiseException;
+import org.kkumulkkum.server.exception.code.PromiseErrorCode;
+import org.kkumulkkum.server.service.participant.ParticipantRetriever;
 import org.kkumulkkum.server.service.participant.ParticipantSaver;
-import org.kkumulkkum.server.service.member.MemberRetreiver;
+import org.kkumulkkum.server.service.userInfo.UserInfoRetriever;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.time.Duration;
+import java.time.LocalDateTime;
 import java.util.List;
 
 @Service
@@ -24,6 +26,8 @@ public class PromiseService {
     private final PromiseRetriever promiseRetriever;
     private final PromiseEditor promiseEditor;
     private final ParticipantSaver participantSaver;
+    private final ParticipantRetriever participantRetriever;
+    private final UserInfoRetriever userInfoRetriever;
     private final EntityManager entityManager;
 
     @Transactional
@@ -55,10 +59,19 @@ public Long createPromise(Long userId, Long meetingId, PromiseCreateDto createPr
     }
 
     @Transactional
-    public void completePromise(Long userId, Long promiseId) {
-        // TODO: PARTICIPANT 검증
+    public void completePromise(Long promiseId) {
         Promise promise = promiseRetriever.findById(promiseId);
+        if (promise.getTime().isAfter(LocalDateTime.now())) {
+            throw new PromiseException(PromiseErrorCode.NOT_PAST_DUE);
+        }
+
+        if (promiseRetriever.existsByArrivedAtIsNull(promiseId)) {
+            throw new PromiseException(PromiseErrorCode.NOT_ARRIVED_PARTICIPANT_EXISTS);
+        }
+
         promiseEditor.completePromise(promise);
+        List<Participant> participants = participantRetriever.findAllByPromiseId(promiseId);
+        participants.forEach(participant -> updateUserInfo(participant, promise.getTime()));
     }
 
     @Transactional(readOnly = true)
@@ -77,4 +90,16 @@ public PromiseDto getPromise(
         Promise promise = promiseRetriever.findById(promiseId);
         return PromiseDto.from(promise);
     }
+
+    private void updateUserInfo(Participant participant, LocalDateTime promiseTime) {
+        UserInfo userInfo = userInfoRetriever.findByParticipantId(participant.getId());
+        userInfo.addPromiseCount();
+        if (promiseTime.isBefore(participant.getArrivalAt())) {
+            userInfo.addLateCount();
+            userInfo.addLateTime(Duration.between(promiseTime, participant.getArrivalAt()).getSeconds());
+        } else {
+            userInfo.levelUp();
+        }
+    }
+
 }
diff --git a/src/main/java/org/kkumulkkum/server/service/userInfo/UserInfoRetriever.java b/src/main/java/org/kkumulkkum/server/service/userInfo/UserInfoRetriever.java
index 4088242..9f04945 100644
--- a/src/main/java/org/kkumulkkum/server/service/userInfo/UserInfoRetriever.java
+++ b/src/main/java/org/kkumulkkum/server/service/userInfo/UserInfoRetriever.java
@@ -17,4 +17,9 @@ public UserInfo findByUserId(final Long id) {
         return userInfoRepository.findByUserId(id)
                 .orElseThrow(() -> new UserException(UserErrorCode.NOT_FOUND_USER));
     }
+
+    public UserInfo findByParticipantId(final Long id) {
+        return userInfoRepository.findByParticipantId(id)
+                .orElseThrow(() -> new UserException(UserErrorCode.NOT_FOUND_USER));
+    }
 }