It is generally known that the air-flow between the air-hole and the bearing clearance of the air-lubricated bearing is equivalent to the air-flow through a nozzle. In this case, when a restrictor that corresponds to the air-hole and bearing clearance is set before the air-hole, the pressure in front of the air-hole will increase or decrease with the decrease or increase of the bearing clearance same as the gage pressure in the high pressure type pneumatic gage, and then the eccentric motion of shaft will be controlled automatically. Then these effects of a restrictor before the air-hole were clarified by measuring the coefficient of friction, and the cross-sectional area of the restrictor and the air-supply pressure were determined for these effects.