diff --git a/.github/workflows/pr-opened.yml b/.github/workflows/pr-opened.yml
new file mode 100644
index 0000000..90141bc
--- /dev/null
+++ b/.github/workflows/pr-opened.yml
@@ -0,0 +1,40 @@
+name: PR Opened - Auto Review
+
+on:
+  pull_request:
+    types: [opened, synchronize]
+
+jobs:
+  auto-review:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+      contents: read
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Add PR labels
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const labels = ['👀 state:reviewing', '🎯 phase:review'];
+
+            await github.rest.issues.addLabels({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.payload.pull_request.number,
+              labels: labels
+            });
+
+      - name: Comment on PR
+        uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.payload.pull_request.number,
+              body: '🤖 自動レビュー開始\n\nコードレビューを実施しています...'
+            });