The present invention provides as an aspect thereof an accessory apparatus detachably attachable to an image-capturing apparatus. The accessory apparatus includes an accessory communicator configured to enable communication with the image-capturing apparatus, and an accessory controller configured to perform the communication with the image-capturing apparatus through the accessory communicator. The accessory controller is configured, in response to detecting an error in the communication, to transmit an error notice that notifies the image-capturing apparatus of the error, and to perform a communication restoration process for restoring the communication, without waiting for a response to the error notice from the image-capturing apparatus.