The motor drive current has a value increased for a time necessary for the clutch operation to mechanically connect the motor and spool and, after the clutch operation, the drive current has a value necessary only for preventing the rotation of the spool due to the belt tension. In this way, the power necessary only for restraining the occupant is consumed after the operation of the clutch is ensured. Then, it is possible to reduce the motor power consumption and suppress heat generation of the motor.