diff --git a/src/oneMonthSchedule.ts b/src/oneMonthSchedule.ts
index 83d6b92..1d25db5 100644
--- a/src/oneMonthSchedule.ts
+++ b/src/oneMonthSchedule.ts
@@ -22,7 +22,9 @@ export default class OneMonthSchedule {
 
     const scheduleJson = await OneMonthSchedule.getScheduleJson(customUrl);
 
-    const scheduleList = JSON.parse(scheduleJson) as ScheduleInterface[];
+    const scheduleList = OneMonthSchedule.normalizeSchedule(
+      JSON.parse(scheduleJson) as ScheduleInterface[]
+    );
 
     console.info(`${date.format('YYYY年MM月')}分の予定を更新します`);
     OneMonthSchedule.delete1MonthCalendarEvents(date, siteCalendarIds);
@@ -118,4 +120,18 @@ export default class OneMonthSchedule {
       )}分時点のカレンダー作成回数: ${counter.getCreateEventCallCount()}`
     );
   }
+
+  /**
+   *
+   * @param {ScheduleInterface[]} scheduleList
+   * @returns {{date: string, description?: string, startTime?: string, endTime: string | undefined, title: string, type: string}[]}
+   */
+  private static normalizeSchedule(scheduleList: ScheduleInterface[]) {
+    return scheduleList.map((schedule) => {
+      const endTime = dayjs(schedule.startTime).isAfter(dayjs(schedule.endTime))
+        ? undefined
+        : schedule.endTime;
+      return { ...schedule, endTime };
+    });
+  }
 }
diff --git a/tests/oneMonthSchedule.test.ts b/tests/oneMonthSchedule.test.ts
index 0794339..02b149b 100644
--- a/tests/oneMonthSchedule.test.ts
+++ b/tests/oneMonthSchedule.test.ts
@@ -119,4 +119,72 @@ describe('setSchedule', () => {
     );
     expect(UrlFetchApp.fetch).not.toBeCalled();
   });
+  it('スケジュールのデータが開始日時が終了日時よりも後ろにある場合に終了日時は消されること', async () => {
+    const scheduleJson =
+      '[{"title":"欅坂46 こちら有楽町星空放送局","start":"2019-12-01","end":"2019-11-30","className":"media","description":"欅坂46 こちら有楽町星空放送局"}]';
+    UrlFetchApp.fetch = jest.fn(() => ({
+      getContentText: jest.fn(() => scheduleJson),
+    })) as jest.Mock;
+
+    const calendarEventMock = jest.fn(() => ({
+      deleteEvent: jest.fn().mockReturnThis(),
+    }));
+
+    CalendarApp.getCalendarById = jest.fn(() => ({
+      getEventsForDay: jest.fn(() => [calendarEventMock()]),
+    })) as jest.Mock;
+
+    const date = dayjs('2019-12-01');
+    await expect(
+      OneMonthSchedule.setSchedule(
+        date,
+        getKeyakiCalendarUrl,
+        keyakiCalendarIds
+      )
+    ).resolves.not.toThrow();
+    expect(Calendar.createEvent).toBeCalledWith(
+      {
+        className: 'media',
+        description: '欅坂46 こちら有楽町星空放送局',
+        end: '2019-11-30',
+        endTime: undefined,
+        start: '2019-12-01',
+        title: '欅坂46 こちら有楽町星空放送局',
+      },
+      [
+        {
+          calendarId: 'jdnc8uf21242be7qjm5nmj7uok@group.calendar.google.com',
+          type: 'shakehands',
+        },
+        {
+          calendarId: 'eh0boh68ai7r2v15m38k2ms1lg@group.calendar.google.com',
+          type: 'event',
+        },
+        {
+          calendarId: '8l4srrnd9c6vge51k6cclsdsmc@group.calendar.google.com',
+          type: 'goods',
+        },
+        {
+          calendarId: '8tc88j0j9gmr95qa81r8t2210c@group.calendar.google.com',
+          type: 'release',
+        },
+        {
+          calendarId: 'f4bcp8sqv66sugk9m06gb1ioeg@group.calendar.google.com',
+          type: 'ticket',
+        },
+        {
+          calendarId: '9beck0tqd2096b3b5utkh0jg8g@group.calendar.google.com',
+          type: 'media',
+        },
+        {
+          calendarId: 'lihum5fsldhsspa3r8altr01ns@group.calendar.google.com',
+          type: 'birthday',
+        },
+        {
+          calendarId: 'efhfvac7iii073suf8v16tlmic@group.calendar.google.com',
+          type: 'other',
+        },
+      ]
+    );
+  });
 });