A multipath transmission system according to the present invention comprises a plurality of multiplex nodes connected to two multiplex buses. Each of the multiplex nodes is assigned to a specific apparatus, and includes a communication control circuit (LSI) for fetching multiplex signals from the apparatus and transmitting the multiplex signals to the multiplex buses. One multiplex node, out of the plurality of multiplex nodes, includes communication control circuits driver/receiver circuits, and troubleshooting driver/receiver circuits, which are connected to the multiplex buses and used for signal transfer between the buses, and a microprocessor for troubleshooting the multiplex buses and the multiplex nodes. The multiplex node relays a failure signal, corresponding to the result of troubleshooting, to the other network which suffers no trouble.