PURPOSE: To keep off a large noise and vibration in a bearing part at the time of high speed rotation by supporting a rotor shaft with a thrust air bearing and a radial air bearing free of rotation.

CONSTITUTION: Plural line of spiral grooves 13 are formed on the circumference of one end of a rotor shaft 8, while lubricating air between a first bearing part 3 and the rotor shaft 8 is fed, with pressure, toward an inner bottom surface 3a of the first bearing part 3, thereby constituting an air bearing which generates thrust force. A pair of spiral grooves 14a, 14b consisting of plural lines of grooves are formed on the circumference of the other end of the rotor shaft 8 being fitted in the inner part of a second bearing part 4, and lubricating air between the second bearing part 4 and the rotor shaft 8 is fed, with pressure, to an intermediate part between these spiral grooves 14a and 14b, thereby constituting a radial air bearing.