In a camera system according to the invention, a camera body and an interchangeable lens have respective identification data tables that are congruous with each other. As an appropriate data address is indicated to the interchangeable lens by the camera body, an identification data that is stored in the identification data storage section and corresponds to the indicated address is transmitted from the interchangeable lens to the camera body. The identification data judging section of the camera body compares the identification data transmitted back from the interchangeable lens and the identification data that is stored in the identification data storage section and corresponds to the address. As a result, it is determined if the dedicated accessory device is mounted on the camera body or not.