In a power generator provided with a stator frame having a stator iron core incorporating a stator coil therein in an inner portion thereof, and a rotor in which a rotor coil rotating so as to oppose to the stator frame and the stator iron core is incorporated, the power generator is provided with a noise insulation plate fixed to a noise insulation plate attaching seat welded to an outer surface of the stator frame by a bolt and a nut, an elastic body (a gasket) is provided in a contact portion between the noise insulation plate attaching seat and the noise insulation plate, and a vibration-proofing rubber washer is provided in a contact portion between the noise insulation plate and the nut.