For signals to be transmitted through a signal transmission path constituted by a relay device group for relay for each set of a plurality of channels, a timing adjustment unit is provided in both or one of a receiver-side LSI and a transmitter-side LSI for each set of a plurality of channels transmitted through the relay device group for relay so that the signals can be transmitted with accurate timing. In addition, the timing adjustment unit can adjust the timing for signals transmitted through each relay device group, the timing in one receiver-side LSI in signal transmission through a plurality of relay device groups, and the timing in one-to-many signal transmission in which signals are transmitted from one transmitter-side LSI to a plurality of receiver-side LSIs.