Filters output a vibration-suppression gain for suppressing resonance of a sub frame or shimmy by performing a filter processing on a rotational angle of a motor. The filters have respective frequency characteristics that a gain becomes a maximum magnitude and a phase advances by 90° at a cut-off angle frequency. The cut-off angle frequency of the filter is fixedly set at a resonance frequency of the sub frame. The cut-off angle frequency of the filter is variably set in accordance with a tire rotation frequency. A gain adder adds the respective gains of the filters and outputs an added magnitude to a correcting mechanism as a vibration-suppression gain. The correcting mechanism corrects a motor torque set by an assist map by using the vibration-suppression gain outputted by the gain adder.