An output shaft (80) has a shaft hole (83) into which a shaft (200) can be fitted is rotated by torque outputted from a motor (3), and outputs the torque to the shaft (200). A magnet holder (90) has aholder hole (93) into which the shaft (200) can be fitted, and is provided so as to be capable of rotation together with the shaft (200). A magnet (35) is provided to the magnet holder (90). An anglesensor (45) is capable of detecting the magnetic flux from the magnet (35) and is capable of outputting a signal corresponding to the rotational angle of the magnet holder (90). The degree of backlash between the shaft (200) and the shaft hole (83) is set to be not less than a first prescribed value. The degree of backlash between the shaft (200) and the holder hole (93) is set to be not more than a second prescribed value.