diff --git a/README.md b/README.md
index 0a1540d67..7afba718b 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 [![Join the chat at https://gitter.im/mogemimi/pomdog](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/mogemimi/pomdog?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
-Pomdog is an experimental game engine, written in C++20 or later, developed as a hobby.
+Pomdog is an experimental game engine, written in C++23 or later, developed as a hobby.
 It is open source and distributed under the [MIT License](http://opensource.org/licenses/MIT).
 
 * [Homepage](http://enginetrouble.net/pomdog)
diff --git a/cmake/dependencies/catch2/CMakeLists.txt b/cmake/dependencies/catch2/CMakeLists.txt
index b17efd63b..ba8fa732b 100644
--- a/cmake/dependencies/catch2/CMakeLists.txt
+++ b/cmake/dependencies/catch2/CMakeLists.txt
@@ -12,7 +12,7 @@ add_library(catch2_static STATIC
 )
 
 set_target_properties(catch2_static PROPERTIES
-    CXX_STANDARD 20
+    CXX_STANDARD 23
     CXX_STANDARD_REQUIRED ON
     CXX_EXTENSIONS OFF
 )
@@ -61,7 +61,7 @@ set_target_properties(catch2_static PROPERTIES
     XCODE_ATTRIBUTE_ONLY_ACTIVE_ARCH[variant=Debug] "YES"
 
     XCODE_ATTRIBUTE_GCC_C_LANGUAGE_STANDARD "c11"
-    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++20"
+    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2b"
     XCODE_ATTRIBUTE_MACOSX_DEPLOYMENT_TARGET "10.14"
 
     # Symbols
diff --git a/cmake/dependencies/libpng/CMakeLists.txt b/cmake/dependencies/libpng/CMakeLists.txt
index a6b30e719..cb8a8cebf 100644
--- a/cmake/dependencies/libpng/CMakeLists.txt
+++ b/cmake/dependencies/libpng/CMakeLists.txt
@@ -84,7 +84,7 @@ set_target_properties(png PROPERTIES
     XCODE_ATTRIBUTE_COMBINE_HIDPI_IMAGES "YES"
 
     XCODE_ATTRIBUTE_GCC_VERSION "com.apple.compilers.llvm.clang.1_0"
-    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2a"
+    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2b"
     XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++"
     XCODE_ATTRIBUTE_CLANG_ENABLE_OBJC_WEAK "YES"
 
diff --git a/cmake/dependencies/mbedtls/CMakeLists.txt b/cmake/dependencies/mbedtls/CMakeLists.txt
index 47a9e4354..48ed4042d 100644
--- a/cmake/dependencies/mbedtls/CMakeLists.txt
+++ b/cmake/dependencies/mbedtls/CMakeLists.txt
@@ -144,7 +144,7 @@ set_target_properties(mbedtls PROPERTIES
     XCODE_ATTRIBUTE_COMBINE_HIDPI_IMAGES "YES"
 
     XCODE_ATTRIBUTE_GCC_VERSION "com.apple.compilers.llvm.clang.1_0"
-    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2a"
+    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2b"
     XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++"
     XCODE_ATTRIBUTE_CLANG_ENABLE_OBJC_WEAK "YES"
 
diff --git a/cmake/dependencies/stb/CMakeLists.txt b/cmake/dependencies/stb/CMakeLists.txt
index 7e52438dc..fc587a747 100644
--- a/cmake/dependencies/stb/CMakeLists.txt
+++ b/cmake/dependencies/stb/CMakeLists.txt
@@ -14,7 +14,7 @@ add_library(stb_static STATIC
 )
 
 set_target_properties(stb_static PROPERTIES
-    CXX_STANDARD 20
+    CXX_STANDARD 23
     CXX_STANDARD_REQUIRED ON
     CXX_EXTENSIONS OFF
 )
@@ -62,7 +62,7 @@ set_target_properties(stb_static PROPERTIES
     XCODE_ATTRIBUTE_COMBINE_HIDPI_IMAGES "YES"
 
     XCODE_ATTRIBUTE_GCC_VERSION "com.apple.compilers.llvm.clang.1_0"
-    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2a"
+    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2b"
     XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++"
     XCODE_ATTRIBUTE_CLANG_ENABLE_OBJC_WEAK "YES"
 
diff --git a/cmake/dependencies/zlib/CMakeLists.txt b/cmake/dependencies/zlib/CMakeLists.txt
index 80776fb38..7fe10b440 100644
--- a/cmake/dependencies/zlib/CMakeLists.txt
+++ b/cmake/dependencies/zlib/CMakeLists.txt
@@ -86,7 +86,7 @@ set_target_properties(zlib PROPERTIES
     XCODE_ATTRIBUTE_COMBINE_HIDPI_IMAGES "YES"
 
     XCODE_ATTRIBUTE_GCC_VERSION "com.apple.compilers.llvm.clang.1_0"
-    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++17"
+    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2b"
     XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++"
     XCODE_ATTRIBUTE_CLANG_ENABLE_OBJC_WEAK "YES"
 
diff --git a/cmake/pomdog/CMakeLists.txt b/cmake/pomdog/CMakeLists.txt
index ecb7db76e..bd0446c36 100644
--- a/cmake/pomdog/CMakeLists.txt
+++ b/cmake/pomdog/CMakeLists.txt
@@ -64,7 +64,7 @@ include(signals.cmake)
 include(utility.cmake)
 
 set_target_properties(pomdog_static PROPERTIES
-    CXX_STANDARD 20
+    CXX_STANDARD 23
     CXX_STANDARD_REQUIRED ON
     CXX_EXTENSIONS OFF
 
@@ -344,7 +344,7 @@ set_target_properties(pomdog_static PROPERTIES
 
     XCODE_ATTRIBUTE_GCC_VERSION "com.apple.compilers.llvm.clang.1_0"
     XCODE_ATTRIBUTE_GCC_C_LANGUAGE_STANDARD "c11"
-    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++20"
+    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2b"
     XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++"
     XCODE_ATTRIBUTE_MACOSX_DEPLOYMENT_TARGET "10.14"
 
diff --git a/examples/feature_showcase/CMakeLists.txt b/examples/feature_showcase/CMakeLists.txt
index 51aa3438e..1dc085b81 100644
--- a/examples/feature_showcase/CMakeLists.txt
+++ b/examples/feature_showcase/CMakeLists.txt
@@ -139,7 +139,7 @@ target_sources(${PRODUCT_NAME} PRIVATE
 )
 
 set_target_properties(${PRODUCT_NAME} PROPERTIES
-    CXX_STANDARD 20
+    CXX_STANDARD 23
     CXX_STANDARD_REQUIRED ON
     CXX_EXTENSIONS OFF
 )
@@ -274,7 +274,7 @@ set_target_properties(${PRODUCT_NAME} PROPERTIES
 
     XCODE_ATTRIBUTE_GCC_VERSION "com.apple.compilers.llvm.clang.1_0"
     XCODE_ATTRIBUTE_GCC_C_LANGUAGE_STANDARD "c11"
-    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++20"
+    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2b"
     XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++"
     XCODE_ATTRIBUTE_MACOSX_DEPLOYMENT_TARGET "10.14"
 
diff --git a/examples/pong/CMakeLists.txt b/examples/pong/CMakeLists.txt
index 32a653c45..835e6aab2 100644
--- a/examples/pong/CMakeLists.txt
+++ b/examples/pong/CMakeLists.txt
@@ -52,7 +52,7 @@ target_sources(${PRODUCT_NAME} PRIVATE
 )
 
 set_target_properties(${PRODUCT_NAME} PROPERTIES
-    CXX_STANDARD 20
+    CXX_STANDARD 23
     CXX_STANDARD_REQUIRED ON
     CXX_EXTENSIONS OFF
 )
@@ -187,7 +187,7 @@ set_target_properties(${PRODUCT_NAME} PROPERTIES
 
     XCODE_ATTRIBUTE_GCC_VERSION "com.apple.compilers.llvm.clang.1_0"
     XCODE_ATTRIBUTE_GCC_C_LANGUAGE_STANDARD "c11"
-    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++20"
+    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2b"
     XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++"
     XCODE_ATTRIBUTE_MACOSX_DEPLOYMENT_TARGET "10.14"
 
diff --git a/examples/quickstart/CMakeLists.txt b/examples/quickstart/CMakeLists.txt
index 68bd42c86..f0342ccdc 100644
--- a/examples/quickstart/CMakeLists.txt
+++ b/examples/quickstart/CMakeLists.txt
@@ -52,7 +52,7 @@ target_sources(${PRODUCT_NAME} PRIVATE
 )
 
 set_target_properties(${PRODUCT_NAME} PROPERTIES
-    CXX_STANDARD 20
+    CXX_STANDARD 23
     CXX_STANDARD_REQUIRED ON
     CXX_EXTENSIONS OFF
 )
@@ -187,7 +187,7 @@ set_target_properties(${PRODUCT_NAME} PROPERTIES
 
     XCODE_ATTRIBUTE_GCC_VERSION "com.apple.compilers.llvm.clang.1_0"
     XCODE_ATTRIBUTE_GCC_C_LANGUAGE_STANDARD "c11"
-    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++20"
+    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2b"
     XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++"
     XCODE_ATTRIBUTE_MACOSX_DEPLOYMENT_TARGET "10.14"
 
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index c9f0a6a6b..e507478ce 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -100,7 +100,7 @@ target_sources(pomdog_test PRIVATE
 )
 
 set_target_properties(pomdog_test PROPERTIES
-    CXX_STANDARD 20
+    CXX_STANDARD 23
     CXX_STANDARD_REQUIRED ON
     CXX_EXTENSIONS OFF
 )
@@ -208,7 +208,7 @@ set_target_properties(pomdog_test PROPERTIES
 
     XCODE_ATTRIBUTE_GCC_VERSION "com.apple.compilers.llvm.clang.1_0"
     XCODE_ATTRIBUTE_GCC_C_LANGUAGE_STANDARD "c11"
-    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++20"
+    XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++2b"
     XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++"
     XCODE_ATTRIBUTE_MACOSX_DEPLOYMENT_TARGET "10.14"