Patent ID: 8221052

Claim:
A turbo-molecular pump comprising: a rotor which is formed with a plurality of rotating blades in a multistage arrangement, and adapted to be rotated at a high speed so as to perform an evacuation operation, said rotor including a first cylindrical body formed with a part of said plurality of rotating blades; a second cylindrical body integrally connected to an outer peripheral region of a downstream end of said first cylindrical body, and formed with the remaining rotating blades; a screw rotor portion which extends from said second cylindrical body along a direction of a rotation axis of said rotor; and a stress-releasing protrusion which extends from the downstream end of said first cylindrical body along the direction of the rotation axis of said rotor; and a first screw stator which extends to have a distal edge located between said screw rotor portion and said protrusion; and a second screw stator which extends to have a distal edge located on an opposite side of said screw rotor portion with respect to said first screw stator portion.