An evacuated casing (2) has outer and inner tubes (2a, 2b) respectively covering the outer and inner peripheries of a hollow cylindrical rotor (6). Ring members (8a, 8b) of a ferromagnetic material are provided in the inner wall of the rotor (6) and face permanent magnets (12a, 12b), which are provided on the inner periphery of the inner tube (2b) and are magnetized in the radial directions of the rotor (6). The permanent magnets (12a, 12b) are fitted on a cylindrical yoke (10) between first and second poles (10a, 10b, 10c) formed thereon, the fluxes being inserted in the rotor (6) via the inner tube (2b). The first poles (10a, 10c) are disposed to face the respective ring members (8a, 8b) while the second pole (10b) is disposed to face the opposed end faces (8a', 8b') of the ring members (8a, 8b). With this arrangement, contactless magnetic bearings are formed to support the rotor (6) stably.