The invention intends to improve a stator which is detachably installed to an outer peripheral portion of a can accommodating a rotor. The stator is integrally formed with a resin mold by arranging a stator assembly (110) within metal molds (300, 310) and injecting a molten resin (P1) from a gate (G1) at one position. An annular plate (160) is mounted to an upper portion of the stator assembly (110) so as to prevent the molten resin from intruding into magnetic pole teeth (120a, 122a), and prevent a weld line from being generated in an outer peripheral surface of the resin mold.