The accessory apparatus provides, with an image-capturing apparatus, a notification channel used for providing a notice from the image-capturing apparatus to the accessory apparatus, a first data communication channel used for data transmission from the accessory apparatus to the image-capturing apparatus, and a second data communication channel used for data transmission from the image-capturing apparatus to the accessory apparatus. An accessory controller acquires from a timer, in response to receiving a transmission request as the notice, a first time of receiving the transmission request and acquires, in response to receiving a specific command through the second data communication channel from the image-capturing apparatus, accessory information corresponding to the first time or a second time acquired based on the first time. The accessory controller transmits the accessory information to the image-capturing apparatus through the first data communication channel.