An on-vehicle alternator is disclosed having a rotor driven by an engine via a belt, a stator having armature windings to generate electromotive forces in response to rotating magnetic fluxes, a housing on which the stator is fixedly secured, a pulley fixedly supported on the rotor to transmit a belt drive force to the rotor, and bearings rotatably supporting the rotor and fixedly supported on the housing. The power generator also includes a bush, formed of a metallic member, which is accommodated in the housing. The bearing, disposed in an area closer to the pulley, is comprised of an inner race, an outer race and rolling elements, all of which are formed of metallic members, with the outer race being press fitted to the bush with a certain degree of interference.