PURPOSE: To reduce axial vibration and to improve the reliability of a device by arranging an inner ring of a thrust load supporting magnetic bearing on the fixed side, fixing an outer ring to the rotary assembly body side and specifying the diameter and length of a journal part.

CONSTITUTION: Herringbone grooves 42 inclined in the rotating direction of the rotary assembly body 50 are engraved on the journal part with several μm depth from the upper and lower ends to the approximately center part. In addition, a fixed side magnetic ring 43 of the thrust load supporting magnetic bearing is externally fitted with a small diameter part formed on the lower side of the journal part 41 and fixed with a bonding agent or the like. When the diameter of the journal part 41 is (d) and the length is l, l/d>0.75 is satisfied. Consequently, axial vibration can be kept within a prescribed value.