To actualize the reduction of parts in number and an enhancement of assembling operations while a dust prevention and water proofing effect is kept constant, and furthermore, enhance a cooling efficiency and a air blowing efficiency.

A case end face plate 22 is mounted at the one end opening part 21a of a case main body 21, and a stator unit 32 having a stator coil 31 is housed in the case main body 21. The rotor shaft 28 of a rotor unit 33 located at the inner side of the stator unit 32, is supported by bearings 26 and 27 mounted on bearing mounting parts 21b and 22b respectively, a centrifugal fan 29 is fixed to the end of the rotor shaft 28 passing through the bearing mounting part 22a, and a fan cover 30 is mounted at the one end opening part 21a in such a way that the centrifugal fan 29 and the case end face plate 22 are enclosed. And a stator coil 31 and an electrical system unit are covered by a resin mold 44, and concurrently, the exposed part of the bearing 26 is covered by a sealing material 36.