diff --git a/frontend/src/components/BuyDialog.tsx b/frontend/src/components/BuyDialog.tsx
index 0d37efb..6acfdd3 100644
--- a/frontend/src/components/BuyDialog.tsx
+++ b/frontend/src/components/BuyDialog.tsx
@@ -12,6 +12,13 @@ import { NewStock } from '../types/types';
 import DatePicker, { registerLocale } from 'react-datepicker';
 import { ja } from 'date-fns/locale/ja'; // date-fnsの日本語ロケールをインポート
 
+// 日付をyyyy-MM-dd形式で返す関数
+const formatDateLocal = (date: Date) => {
+  const year = date.getFullYear();
+  const month = (date.getMonth() + 1).toString().padStart(2, '0');
+  const day = date.getDate().toString().padStart(2, '0');
+  return `${year}-${month}-${day}`;
+};
 
 // 日本語ロケールを登録
     registerLocale('ja', ja);
@@ -59,7 +66,7 @@ const BuyDialog = ({
                             popperClassName="custom-datepicker-popper"
                             selected={newStock.buyDate ? new Date(newStock.buyDate) : null}
                             onChange={(date) =>
-                                setNewStock({ ...newStock, buyDate: date ? date.toISOString().split('T')[0] : '' })
+                                setNewStock({ ...newStock, buyDate: date ? formatDateLocal(date) : '' })
                             }
                             dateFormat="yyyy/MM/dd"
                             customInput={
@@ -86,7 +93,7 @@ const BuyDialog = ({
                             popperClassName="custom-datepicker-popper"
                             selected={newStock.expDate ? new Date(newStock.expDate) : null}
                             onChange={(date) =>
-                                setNewStock({ ...newStock, expDate: date ? date.toISOString().split('T')[0] : '' })
+                                setNewStock({ ...newStock, expDate: date ? formatDateLocal(date) : '' })
                             }
                             dateFormat="yyyy/MM/dd"
                             customInput={