A sensor (110) detects the angle of the output shaft (101a) of a synchronous motor (101). A multiple rotation processing unit (301) converts the angle of one rotation or more that is detected by the sensor (110) into a multiple rotation angle. A phase difference FB unit (305) performs feedback control in such a way that the phase difference between the electrical angle and the mechanical angle of the synchronous motor (101) is a target phase difference (306). A position FB unit (302) performs feedback control in such a way that the multiple rotation angle after conversion by the multiple rotation processing unit (301) is a target position (303).