PURPOSE: To make a radial bearing situated nearer a thrust bearing in small size and light in weight, that should serve to have a small-sized and lightweight pump as a whole, by constituting the thrust bearing with a control electromagnet, fixed on the housing side, and a yoke installed at the end part of rotor on its high vacuum chamber side.

CONSTITUTION: A thrust bearing situated in a high vacuum chamber 15 is composed of a control electromagnet 24 mounted on the housing 11 side, a ferromagnetic yoke 25 installed mating this magnet 24 at the end part of rotor 13 on its high vacuum chamber side, and a thrust position sensor 26. Coil 27 is sealed by a non-magnetic metal member 28 and a sealing member 29, which serve for prevention of detrimental gas for performance of a turbo molecular pump from releasing out of a coil covering. Owing to provision of this thrust magnetic bearing (24, 25), the gravity of rotor in its axial direction is borne evenly by two radial bearings, and the forces applied to the bearings become approx. equal. Thus the radial bearing situated nearer to the thrust bearing can be made in small size and light-weight.