diff --git a/__test__/example.http b/__test__/example.http
index 1067b8ef..37ce8344 100644
--- a/__test__/example.http
+++ b/__test__/example.http
@@ -10,7 +10,7 @@ GET http://localhost:3000/api/users HTTP/1.1
 
 ###
 
-GET http://localhost:3000/api/users/127 HTTP/1.1
+GET http://localhost:3000/api/users/10 HTTP/1.1
 
 ###
 
@@ -24,7 +24,7 @@ Content-Type: application/json
 
 ###
 
-PUT http://localhost:3000/api/users/127 HTTP/1.1
+PUT http://localhost:3000/api/users/37 HTTP/1.1
 Content-Type: application/json
 
 {
@@ -34,7 +34,7 @@ Content-Type: application/json
 
 ###
 
-DELETE http://localhost:3000/api/users/127 HTTP/1.1
+DELETE http://localhost:3000/api/users/37 HTTP/1.1
 
 ###
 # 投稿一覧取得
@@ -42,7 +42,7 @@ GET http://localhost:3000/api/posts HTTP/1.1
 
 ###
 # 特定の投稿を取得
-GET http://localhost:3000/api/posts/36 HTTP/1.1
+GET http://localhost:3000/api/posts/5 HTTP/1.1
 
 ###
 # 投稿を作成
@@ -53,12 +53,12 @@ Content-Type: application/json
   "title": "Test Post",
   "body": "This is a test post.",
   "tags": ["test", "example"],
-  "author_id": 182
+  "author_id": 10
 }
 
 ###
 # 投稿を更新
-PUT http://localhost:3000/api/posts/36 HTTP/1.1
+PUT http://localhost:3000/api/posts/6 HTTP/1.1
 Content-Type: application/json
 
 {
@@ -69,4 +69,4 @@ Content-Type: application/json
 
 ###
 # 投稿を削除
-DELETE http://localhost:3000/api/posts/36 HTTP/1.1
+DELETE http://localhost:3000/api/posts/6 HTTP/1.1
diff --git a/__test__/posts.test.ts b/__test__/posts.tests.ts
similarity index 79%
rename from __test__/posts.test.ts
rename to __test__/posts.tests.ts
index 15606b5c..40d8ae07 100644
--- a/__test__/posts.test.ts
+++ b/__test__/posts.tests.ts
@@ -18,6 +18,15 @@ describe('Posts API', () => {
     userId = user.id;
   });
 
+  afterEach(async () => {
+    await prisma.$transaction([
+      prisma.postTag.deleteMany(),
+      prisma.tag.deleteMany(),
+      prisma.post.deleteMany(),
+      prisma.user.deleteMany(),
+    ]);
+  });
+
   it('should create a post and return 201 status', async () => {
     const requestBody = JSON.stringify({
       title: 'Test Post',
@@ -138,4 +147,40 @@ describe('Posts API', () => {
 
     expect(deleteResponse.status).toBe(204);
   });
+
+  it('should return 404 when trying to update a non-existent post', async () => {
+    const updateRequestBody = JSON.stringify({
+      title: 'Non-existent Post',
+      body: 'This post does not exist.',
+      tags: ['nonexistent'],
+    });
+    const updateRequest = new Request(
+      `http://localhost:3000/api/posts/999999`,
+      {
+        method: 'PUT',
+        body: updateRequestBody,
+      },
+    );
+
+    const updateResponse = await PUT(updateRequest, {
+      params: { id: '999999' },
+    });
+
+    expect(updateResponse.status).toBe(404);
+  });
+
+  it('should return 404 when trying to delete a non-existent post', async () => {
+    const deleteRequest = new Request(
+      `http://localhost:3000/api/posts/999999`,
+      {
+        method: 'DELETE',
+      },
+    );
+
+    const deleteResponse = await DELETE(deleteRequest, {
+      params: { id: '999999' },
+    });
+
+    expect(deleteResponse.status).toBe(404);
+  });
 });
diff --git a/__test__/users.test.ts b/__test__/users.test.ts
index 5acf3d80..e8d3f0c6 100644
--- a/__test__/users.test.ts
+++ b/__test__/users.test.ts
@@ -40,6 +40,8 @@ describe('Users API', () => {
 
     const createResponse = await POST(createRequest);
     const createdUser = await createResponse.json();
+    console.debug(createdUser);
+    console.debug(createdUser.id);
 
     const response = await GET_ID(
       new Request(`http://localhost:3000/api/users/${createdUser.id}`),
diff --git a/package.json b/package.json
index eb9721ba..bfb0e18f 100644
--- a/package.json
+++ b/package.json
@@ -19,7 +19,7 @@
     "format:check": "prettier --check .",
     "prepare": "husky install",
     "db:seed": "npx prisma db seed --schema ./src/app/prisma/schema.prisma",
-    "db:setup": "npx prisma generate --schema ./src/app/prisma/schema.prisma",
+    "db:generate": "npx prisma generate --schema ./src/app/prisma/schema.prisma",
     "db:drop": "npx prisma db query 'DROP DATABASE your_database_name' --schema ./src/app/prisma/schema.prisma",
     "db:migrate": "npx prisma migrate dev --schema ./src/app/prisma/schema.prisma",
     "db:reset": "npx prisma migrate reset --schema ./src/app/prisma/schema.prisma",
diff --git a/src/app/api/posts/[id]/route.ts b/src/app/api/posts/[id]/route.ts
index d3d45d54..a1acde25 100644
--- a/src/app/api/posts/[id]/route.ts
+++ b/src/app/api/posts/[id]/route.ts
@@ -38,6 +38,15 @@ export async function PUT(
   { params }: { params: { id: string } },
 ) {
   try {
+    const postId = parseInt(params.id, 10);
+    const existingPost = await prisma.post.findUnique({
+      where: { id: postId },
+    });
+
+    if (!existingPost) {
+      return NextResponse.json({ message: 'Post not found' }, { status: 404 });
+    }
+
     const { title, body, draft, notice, tags, scope, published_at } =
       await request.json();
 
@@ -55,7 +64,7 @@ export async function PUT(
     }
 
     const post = await prisma.post.update({
-      where: { id: parseInt(params.id, 10) },
+      where: { id: postId },
       data: {
         title,
         body,
@@ -72,7 +81,7 @@ export async function PUT(
 
     // ポストとタグの関連付けをリセットして再設定
     await prisma.postTag.deleteMany({
-      where: { postId: parseInt(params.id, 10) },
+      where: { postId: postId },
     });
 
     if (tagIds.length > 0) {
@@ -110,11 +119,20 @@ export async function DELETE(
   { params }: { params: { id: string } },
 ) {
   try {
+    const postId = parseInt(params.id, 10);
+    const existingPost = await prisma.post.findUnique({
+      where: { id: postId },
+    });
+
+    if (!existingPost) {
+      return NextResponse.json({ message: 'Post not found' }, { status: 404 });
+    }
+
     await prisma.postTag.deleteMany({
-      where: { postId: parseInt(params.id, 10) },
+      where: { postId: postId },
     });
     await prisma.post.delete({
-      where: { id: parseInt(params.id, 10) },
+      where: { id: postId },
     });
     return new Response(null, { status: 204 });
   } catch (error) {