To prevent the damage of a rotary shaft and a bearing by stopping fluid supply while controlling the supply so gradually to gradually reduce the pressure of fluid within the bearing.

When prescribed time passes from the starting of a valve OFF button of an operation panel and a rotary shaft becomes an inertial revolution state of the number of revolution of about 1000 rpm or below, an inverter 21 of a valve control device 20 starts to close a valve 13 by an actuator 22 by a valve closing command signal. When it takes about 5 to 10 minutes, for instance, to reduce the number of revolution of the rotary shaft from 50000 rpm to 1000 rpm, the valve 13 starts to close after about 5 to 10 minutes after the valve OFF button is started and pressure reduction is gradually performed for air within an air bearing. When pressure within the air bearing in which the rotary shaft seats on the air bearing is reduced from 2.0 kgf/cm2 to 0.5 kgf/cm2 in a pressure reduction process for about 5 seconds or more, the air bearing little vibrates or nearly vibrates, even if the rotary shaft comes into contact with the bearing, and the air bearing and the rotary shaft are not damaged.