A stator includes two yokes and two coils. Each yoke is a claw pole type and has a plurality of pole teeth, which extend in an axial direction. The yokes are axially opposed to each other in such a manner that the pole teeth of one of the yokes and the pole teeth of the other one of the yokes are alternately arranged in a circumferential direction. The coils are circumferentially wound to form two phases, respectively, and are arranged between the yokes. A rotor includes a plurality of rotor magnets, each of which provides a magnetic pole. A single magnetic position sensor senses a rotational position of the rotor and outputs a position measurement signal, which indicates the sensed rotational position of the rotor. A half-wave electric current is alternately supplied to the coils based on the position measurement signal.