A motor stator section (3a) is furnished with a busbar (51) attached to an armature (3), and with a circuit board (52) attached to the busbar (51). A parts accommodation recess (516) is formed in the busbar (51) surface that opposes the circuit board (52), and a holding recess (512), in which is anchored a sensor holder (54) that retains Hall sensors (53) mounted on the circuit board (52) is formed in the busbar (51) inner circumferential surface. Further, grooves are formed in the circuit board (52), the sensor holder (54), and the busbar (51), wherein fitting a jig (9) to these grooves enables high-precision assembly of these components.