A microcomputer includes an abnormality monitor unit, a rotation angle calculation unit and a current supply control unit. The abnormality monitor unit monitors an abnormality of the rotation angle sensor. The rotation angle calculation unit calculates an electrical angle based on angle information acquired from the rotation angle sensor and an abnormality state of the rotation angle sensor. The current supply control unit controls current supply to the winding sets based on the electrical angle. When an abnormality is detected in one of the sensor units, the rotation angle calculation unit calculates the electrical angle based on a hold value which is the electrical angle before the detection of abnormality during a period from the detection of abnormality to a final determination of the abnormality. When the abnormality of the sensor unit is finalized, the electrical angle is calculated based on the angle information of the other sensor unit which is normal.