Abstract: A vehicle multiplex transmission apparatus which can operate all the auxiliary units of a vehicle even when a power supply line of the vehicle is locally short-circuited. This vehicle multiplex transmission apparatus includes a plurality of control nodes arranged in respective portions of a vehicle, for controlling vehicle auxiliary units, and a multiplex transmission line for connecting among the plurality of control nodes. The control nodes are connected to a power supply node arranged at a predetermined position of a vehicle body through two independent systems of first and second power supply lines. The first power supply line supplies power to vehicle travel auxiliary units. The second power supply line supplies power to general system auxiliary units, but it can supply power to the travel auxiliary units as needed.