An imaging apparatus that provides, between itself and an accessory device, a notification channel used for notification from the imaging apparatus to the accessory device, a first data communication channel used in data transmission from the accessory device to the imaging apparatus, and a second data communication channel used in data transmission from the imaging apparatus to the accessory device. An accessory control unit executes switching of communication methods while notifying the imaging apparatus of a communication standby request for keeping data communication from the imaging apparatus to the accessory device from being performed, via the notification channel.