Vehicular network device

Two communication ECUs which can be disposed in different areas on a vehicle are equipped with respective communication relays which are connected to each other by an interarea connection unit. The functions of each of the communication relays are simplified and separated from the functions of a router. When receiving a signal, the communication relays outputs the signal to another, belonging to the same system as the communication line from which the signal has been received, of communication lines and to the router. The router controls a route of a signal to be transmitted between different systems of communication lines that are one of the communication lines and one of the communication lines. Since the communication relays are low in cost and can operate at high speed and the number of routers is decreased, the components cost can be lowered.