Each ECU in a system configuration based on a motorized seatbelt retractor having an ECU combined with a motor shortens the harness length along which many currents flow as much as possible. A main ECU and a subsidiary ECU each have functions corresponding to those are provided to a control unit for controlling a motor for a motorized seatbelt retractor. The main ECU determines output start conditions and transmits commands, and the subsidiary ECU autonomously performs detailed motor current control and the like.