A vacuum pump has a pump case (1) forming a gas suction port (2) at the upper surface thereof; a rotor shaft (5) rotatably supported in the pump case; a rotor (8) being formed a corrosion-resistant film treated by nonelectrolytic plating on the inner and outer circumferential surfaces (8b, 8a) of the rotor; a plurality of rotor blades (10) accommodated in the pump case and integrally formed with an outer circumferential surface of the rotor; a plurality of stator blades (11) fixed in the pump case such that the rotor blades and the stator blades are alternately positioned and arranged; a drive motor (9) for rotating the rotor shaft; and mass-addition means (15) formed by applying an adhesive or a coating, having heat and corrosion resistances, on the inner circumferential surface of the rotor. <IMAGE>
