diff --git a/task_yell/src/lib/events.ts b/task_yell/src/lib/events.ts
index 2de88aa..16b7a4b 100644
--- a/task_yell/src/lib/events.ts
+++ b/task_yell/src/lib/events.ts
@@ -14,35 +14,36 @@ const COLLECTION_NAME = "events";
  * @param event 作成されるイベント
  * @returns 競合がない場合はnull, そうでない場合はマージエディターで必要なので該当日時のイベントのリスト
  */
-export async function createEvent(event: Event): Promise<Event[] | null> {
+export async function createEvent(userId: string, event: Event): Promise<Event[] | null> {
   // event.start ~ event.end とコンフリクトする予定があるかどうかを確認する
-  const events = await readEvents();
+  const events = await readEvents(userId);
   const isConflict = events.some(
     (e) => event.start <= e.end && event.end >= e.start,
   );
   if (isConflict) {
     return events;
   } else {
-    await createData<Event>(COLLECTION_NAME, event);
+    await createData<Event>(`users/${userId}/${COLLECTION_NAME}`, event);
     return null;
   }
 }
 
-export async function readEvents(): Promise<Event[]> {
-  return readData<Event>(COLLECTION_NAME);
+export async function readEvents(userId: string): Promise<Event[]> {
+  return readData<Event>(`users/${userId}/${COLLECTION_NAME}`);
 }
 
-export async function readSingleEvent(id: string): Promise<Event | null> {
-  return readSingleData<Event>(COLLECTION_NAME, id);
+export async function readSingleEvent(userId: string, id: string): Promise<Event | null> {
+  return readSingleData<Event>(`users/${userId}/${COLLECTION_NAME}`, id);
 }
 
 export async function updateEvent(
+  userId: string,
   id: string,
   eventData: Partial<Event>,
 ): Promise<void> {
-  return updateData<Event>(COLLECTION_NAME, id, eventData);
+  return updateData<Event>(`users/${userId}/${COLLECTION_NAME}`, id, eventData);
 }
 
-export async function deleteEvent(id: string): Promise<void> {
-  return deleteData(COLLECTION_NAME, id);
+export async function deleteEvent(userId: string, id: string): Promise<void> {
+  return deleteData(`users/${userId}/${COLLECTION_NAME}`, id);
 }
diff --git a/task_yell/src/lib/tasks.ts b/task_yell/src/lib/tasks.ts
index c9065f9..430a016 100644
--- a/task_yell/src/lib/tasks.ts
+++ b/task_yell/src/lib/tasks.ts
@@ -14,8 +14,8 @@ const COLLECTION_NAME = "tasks";
  *
  * @param task 作成されるタスク
  */
-export async function createTask(task: Task): Promise<void> {
-  await createData(COLLECTION_NAME, task);
+export async function createTask(userId: string, task: Task): Promise<void> {
+  await createData(`users/${userId}/${COLLECTION_NAME}`, task);
 }
 
 /**
@@ -23,8 +23,8 @@ export async function createTask(task: Task): Promise<void> {
  *
  * @returns 全タスク
  */
-export async function readTasks(): Promise<Task[]> {
-  return readData<Task>(COLLECTION_NAME);
+export async function readTasks(userId: string): Promise<Task[]> {
+  return readData<Task>(`users/${userId}/${COLLECTION_NAME}`);
 }
 
 /**
@@ -33,8 +33,8 @@ export async function readTasks(): Promise<Task[]> {
  * @param id - 取得するタスクのID。
  * @returns 指定されたIDのタスク。
  */
-export async function readSingleTask(id: string): Promise<Task | null> {
-  return readSingleData<Task>(COLLECTION_NAME, id);
+export async function readSingleTask(userId: string, id: string): Promise<Task | null> {
+  return readSingleData<Task>(`users/${userId}/${COLLECTION_NAME}`, id);
 }
 
 /**
@@ -44,10 +44,11 @@ export async function readSingleTask(id: string): Promise<Task | null> {
  * @param taskData 新規タスクデータ
  */
 export async function updateTask(
+  userId: string,
   id: string,
   taskData: Partial<Task>,
 ): Promise<void> {
-  await updateData<Task>(COLLECTION_NAME, id, taskData);
+  await updateData<Task>(`users/${userId}/${COLLECTION_NAME}`, id, taskData);
 }
 
 /**
@@ -55,6 +56,6 @@ export async function updateTask(
  *
  * @param id 削除するタスクのID。
  */
-export async function deleteTask(id: string): Promise<void> {
-  await deleteData(COLLECTION_NAME, id);
+export async function deleteTask(userId: string, id: string): Promise<void> {
+  await deleteData(`users/${userId}/${COLLECTION_NAME}`, id);
 }
diff --git a/task_yell/src/lib/want-todo.ts b/task_yell/src/lib/want-todo.ts
index 74a96c0..1bc27c7 100644
--- a/task_yell/src/lib/want-todo.ts
+++ b/task_yell/src/lib/want-todo.ts
@@ -13,8 +13,8 @@ const COLLECTION_NAME = "want-todos";
  *
  * @param wantTodo - 作成する `WantTodo` オブジェクト。
  */
-export async function createWantTodo(wantTodo: WantTodo): Promise<void> {
-  await createData<WantTodo>(COLLECTION_NAME, wantTodo);
+export async function createWantTodo(userId: string, wantTodo: WantTodo): Promise<void> {
+  await createData<WantTodo>(`users/${userId}/${COLLECTION_NAME}`, wantTodo);
 }
 
 /**
@@ -22,8 +22,8 @@ export async function createWantTodo(wantTodo: WantTodo): Promise<void> {
  *
  * @returns 全WantTodo
  */
-export async function readWantTodos(): Promise<WantTodo[]> {
-  return readData<WantTodo>(COLLECTION_NAME);
+export async function readWantTodos(userId: string): Promise<WantTodo[]> {
+  return readData<WantTodo>(`users/${userId}/${COLLECTION_NAME}`);
 }
 
 /**
@@ -32,8 +32,8 @@ export async function readWantTodos(): Promise<WantTodo[]> {
  * @param id - 取得するイベントのID。
  * @returns 指定されたIDのWantTodo。
  */
-export async function readSingleWantTodo(id: string): Promise<WantTodo | null> {
-  return readSingleData<WantTodo>(COLLECTION_NAME, id);
+export async function readSingleWantTodo(userId: string, id: string): Promise<WantTodo | null> {
+  return readSingleData<WantTodo>(`users/${userId}/${COLLECTION_NAME}`, id);
 }
 
 /**
@@ -43,10 +43,11 @@ export async function readSingleWantTodo(id: string): Promise<WantTodo | null> {
  * @param wantTodoData 新規WantTodoデータ。
  */
 export async function updateWantTodo(
+  userId: string,
   id: string,
   wantTodoData: Partial<WantTodo>,
 ): Promise<void> {
-  return updateData<WantTodo>(COLLECTION_NAME, id, wantTodoData);
+  return updateData<WantTodo>(`users/${userId}/${COLLECTION_NAME}`, id, wantTodoData);
 }
 
 /**
@@ -54,6 +55,6 @@ export async function updateWantTodo(
  *
  * @param id - 削除するWantTodoのID。
  */
-export async function deleteWantTodo(id: string): Promise<void> {
-  return deleteData(COLLECTION_NAME, id);
+export async function deleteWantTodo(userId: string, id: string): Promise<void> {
+  return deleteData(`users/${userId}/${COLLECTION_NAME}`, id);
 }