diff --git a/docs/_pages/mutation/product_stock.md b/docs/_pages/mutation/product_stock.md
index 1849481..4748b96 100644
--- a/docs/_pages/mutation/product_stock.md
+++ b/docs/_pages/mutation/product_stock.md
@@ -3,4 +3,114 @@ layout: home
 author_profile: true
 permalink: /mutation/product_stock
 ---
-商品在庫の更新
+
+## 商品在庫の更新
+
+updateProductStock で商品在庫の更新ができます。
+`stock_unlimited: false` の場合は `stock` が必須、`stock_unlimited: true` の場合は `stock` を指定できません。
+
+### スキーマ
+
+```graphql
+type Mutation {
+  updateProductStock(
+    """商品コード"""
+    code: String!
+
+    """在庫数（在庫無制限の場合、0以上の数値を指定）"""
+    stock: Int
+
+    """在庫無制限（無制限は true 、制限は false を指定）"""
+    stock_unlimited: Boolean!
+  ): ProductClass
+}
+```
+
+### 実行例
+
+#### リクエスト（在庫有限）
+
+```graphql
+mutation {
+  updateProductStock (
+    code: "sand-01",
+    stock: 10,
+    stock_unlimited: false
+  ) {
+    code
+    stock
+    stock_unlimited
+  }
+}
+```
+
+#### レスポンス（在庫有限）
+
+```json
+{
+  "data": {
+    "updateProductStock": {
+      "code": "sand-01",
+      "stock": 10,
+      "stock_unlimited": false,
+    }
+  }
+}
+```
+
+#### リクエスト（在庫無限）
+
+```graphql
+mutation {
+  updateProductStock (
+    code: "sand-01",
+    stock_unlimited: true
+  ) {
+    code
+    stock
+    stock_unlimited
+  }
+}
+```
+
+#### レスポンス（在庫無限）
+
+```json
+{
+  "data": {
+    "updateProductStock": {
+      "code": "sand-01",
+      "stock": null,
+      "stock_unlimited": true,
+    }
+  }
+}
+```
+
+#### Variables を利用したリクエスト例
+
+```graphql
+mutation UpdateProductStock(
+    $code: String!,
+    $stock: Int,
+    $unlimited: Boolean!
+  ){
+  updateProductStock (
+    code: $code,
+    stock: $stock,
+    stock_unlimited: $unlimited
+  ) {
+    code
+    stock
+    stock_unlimited
+  }
+}
+```
+
+```json
+{
+	"code": "sand-01",
+	"stock": 10,
+	"unlimited": false
+}
+```