Control device switching system

A can be reliably intercepted data transmission processing to be performed by the communication control unit according to the sleep or power-off state, to obtain a control device switching system that does not generate the abnormal behavior of network anomalies and vehicles. A prior communication control unit ECU1 goes to sleep or power-off state, from among the proxy candidate device ECU2～ECUm, proxy against ECU that is determined to be intercepted by the proxy transmitting capability judging unit 13 to send a request. As a determination reference when proxy transmitting capability judging unit 13 of the ECU1 determines the proxy device, the proxy can process load of each ECU, in proxy can process with importance, or malfunction judgment result, further, or stopped running by performing the determination in the order in consideration of processing importance of each ECU, to prevent the occurrence of the network 6 abnormalities and behavior of the vehicle abnormality. .The