A camera accessory is detachably mounted at a camera body that includes a first body contact point, a second body contact point, a third body contact point, a fourth body contact point and a fifth body contact point and detects disengagement of the camera accessory when the fifth body contact point sustains a signal level corresponding to a first truth value continuously over a length of time equal to or greater than a predetermined time length. In the camera accessory, the accessory-side communication control device executes control so as to ensure that the signal assuming a level corresponding to the first truth value is not continuously output from the fifth accessory contact point any longer than the predetermined time length while the operating voltage supply from the camera body is provided via the first accessory contact point.