A camera comprises a lens unit and a camera body to which the lens unit is attached by a rotational operation. The camera body is provided with terminals including a specific terminal. Arrangement of the specific terminal is different from that of the other terminals. In detaching the lens unit from the camera body, the specific terminal is adapted to be disconnected earlier relative to the other terminals while the other terminals are connected. After the disconnection of the specific terminal has been detected, the other terminals are set to high impedance.