A VGRS device checks whether assist control of an EPS device for assisting steering operation of a steering wheel is being stopped. If the assist control of the EPS device is being stopped, a speed increase ratio is determined so that the rotation angle of the output shaft is less than the rotation angle of the input shaft. A VGRS motor is controlled and driven based on a determined speed increase ratio. Thus, steering operation of the steering wheel can be controlled appropriately so that the steering operation of the steering wheel can be continued with relatively small torque. It is less likely that a driver will erroneously feel that the steering wheel is locked.