diff --git a/packages/zenn-markdown-html/__tests__/custom-syntax/embed/docswell.test.ts b/packages/zenn-markdown-html/__tests__/custom-syntax/embed/docswell.test.ts
new file mode 100644
index 00000000..79707792
--- /dev/null
+++ b/packages/zenn-markdown-html/__tests__/custom-syntax/embed/docswell.test.ts
@@ -0,0 +1,20 @@
+import { describe, test, expect } from 'vitest';
+import markdownToHtml from '../../../src/index';
+
+describe('Docswell', () => {
+  test('should generate docswell html', () => {
+    const html = markdownToHtml(
+      '@[docswell](https://www.docswell.com/slide/LK7J5V/embed)'
+    );
+    expect(html).toContain(
+      '<script async class="docswell-embed" src="https://www.docswell.com/assets/libs/docswell-embed/docswell-embed.min.js" data-src="https://www.docswell.com/slide/LK7J5V/embed" data-aspect="0.5625"></script><div class="docswell-link"></div>'
+    );
+  });
+
+  test('should not generate docswell html with invalid url', () => {
+    const html = markdownToHtml(
+      '@[docswell](https://www.docswell.com/s/ku-suke/LK7J5V-hello-docswell)'
+    );
+    expect(html).toContain('Doscwellのembed用のURLを指定してください');
+  });
+});
diff --git a/packages/zenn-markdown-html/__tests__/matchers/isDocswellUrl.test.ts b/packages/zenn-markdown-html/__tests__/matchers/isDocswellUrl.test.ts
new file mode 100644
index 00000000..158c8887
--- /dev/null
+++ b/packages/zenn-markdown-html/__tests__/matchers/isDocswellUrl.test.ts
@@ -0,0 +1,34 @@
+import { isDocswellUrl } from '../../src/utils/url-matcher';
+import { describe, test, expect } from 'vitest';
+
+describe('isDocswellUrlのテスト', () => {
+  describe('Docswellの埋め込み用URLのとき', () => {
+    test('trueを返すこと', () => {
+      const docswellEmbedUrl = 'https://www.docswell.com/slide/LK7J5V/embed';
+      expect(isDocswellUrl(docswellEmbedUrl)).toBe(true);
+    });
+  });
+
+  describe('Docswellの他の画面のURLのとき', () => {
+    test('falseを返すこと', () => {
+      const docswellUrls = [
+        'https://www.docswell.com/',
+        'https://www.docswell.com/s/ku-suke/LK7J5V-hello-docswell',
+      ];
+
+      docswellUrls.forEach((url) => {
+        expect(isDocswellUrl(url)).toBe(false);
+      });
+    });
+  });
+
+  describe('他のサイトのURLのとき', () => {
+    test('falseを返すこと', () => {
+      const otherSiteUrls = ['https://zenn.dev/', 'https://github.com/'];
+
+      otherSiteUrls.forEach((url) => {
+        expect(isDocswellUrl(url)).toBe(false);
+      });
+    });
+  });
+});