diff --git a/dictation_client/src/features/dictation/operations.ts b/dictation_client/src/features/dictation/operations.ts
index 2cad273..522b6d9 100644
--- a/dictation_client/src/features/dictation/operations.ts
+++ b/dictation_client/src/features/dictation/operations.ts
@@ -565,10 +565,21 @@ export const backupTasksAsync = createAsyncThunk<
         a.click();
         a.parentNode?.removeChild(a);
 
-        // eslint-disable-next-line no-await-in-loop
-        await tasksApi.backup(task.audioFileId, {
-          headers: { authorization: `Bearer ${accessToken}` },
-        });
+        // バックアップ済みに更新
+        try {
+          // eslint-disable-next-line no-await-in-loop
+          await tasksApi.backup(task.audioFileId, {
+            headers: { authorization: `Bearer ${accessToken}` },
+          });
+        } catch (e) {
+          // e ⇒ errorObjectに変換
+          const error = createErrorObject(e);
+          if (error.code === "E010603") {
+            // タスクが削除済みの場合は成功扱いとする
+          } else {
+            throw e;
+          }
+        }
       }
     }
 
@@ -580,8 +591,22 @@ export const backupTasksAsync = createAsyncThunk<
     );
     return {};
   } catch (e) {
-    // e ⇒ errorObjectに変換"
+    // e ⇒ errorObjectに変換
     const error = createErrorObject(e);
+    if (error.code === "E010603") {
+      // 存在しない音声ファイルをダウンロードしようとした場合
+      thunkApi.dispatch(
+        openSnackbar({
+          level: "error",
+          message: getTranslationID(
+            "dictationPage.message.fileAlreadyDeletedError"
+          ),
+        })
+      );
+
+      return thunkApi.rejectWithValue({ error });
+    }
+
     thunkApi.dispatch(
       openSnackbar({
         level: "error",
diff --git a/dictation_client/src/translation/de.json b/dictation_client/src/translation/de.json
index f72b729..5f65907 100644
--- a/dictation_client/src/translation/de.json
+++ b/dictation_client/src/translation/de.json
@@ -636,4 +636,4 @@
       "lowerLayerId": "(de)Lower Layer ID"
     }
   }
-}
\ No newline at end of file
+}
diff --git a/dictation_client/src/translation/en.json b/dictation_client/src/translation/en.json
index cc746f0..6d1eba5 100644
--- a/dictation_client/src/translation/en.json
+++ b/dictation_client/src/translation/en.json
@@ -636,4 +636,4 @@
       "lowerLayerId": "Lower Layer ID"
     }
   }
-}
\ No newline at end of file
+}
diff --git a/dictation_client/src/translation/es.json b/dictation_client/src/translation/es.json
index 94ec1e8..d0c183f 100644
--- a/dictation_client/src/translation/es.json
+++ b/dictation_client/src/translation/es.json
@@ -636,4 +636,4 @@
       "lowerLayerId": "(es)Lower Layer ID"
     }
   }
-}
\ No newline at end of file
+}
diff --git a/dictation_client/src/translation/fr.json b/dictation_client/src/translation/fr.json
index 4f6cf56..0e801cf 100644
--- a/dictation_client/src/translation/fr.json
+++ b/dictation_client/src/translation/fr.json
@@ -636,4 +636,4 @@
       "lowerLayerId": "(fr)Lower Layer ID"
     }
   }
-}
\ No newline at end of file
+}