Abstract: A multipath transmission system for an automobile according to the present invention comprises a plurality of multiplex transmission units connected in parallel with each other to one common bus. Each transmission unit is assigned to one of groups in which various devices attached to the automobile are classified. The transmission unit includes a sending circuit for transmitting the multiple signals from the devices in the group concerned to the other units through the bus. The system further comprises a power source for always applying electric power to the sending circuit of at least one of the multiplex transmission units. Only that multiplex transmission unit to which the electric power is always applied is provided with a bias circuit which sets the potential of the multiple signals on the bus when the multiple signals are supplied from the sending circuits of any multiplex transmission unit to the bus.