A control apparatus is communicably coupled through an in-vehicle communication line to a device. The control apparatus is operative to control an equipment unit installed therein. In the control apparatus, a determining unit receives a request transmitted from the device. The request includes information related to the device and the control apparatus. The determining unit is configured to determine whether the received request corresponds to a previously specified request according to the information of the received request. A changing unit changes a way of transmitting response data against the received request according to a result of the determination, thereby increasing a first responsibility against the received request corresponding to the specified request, as compared with a second responsibility against the received request except for the specified request.