PURPOSE: To enhance regenerating effect of an adsorbent by providing a first changeover valve to an exhaust path joined to the atmosphere of one end side of an air dryer and providing a second changeover valve to an air communication path jointed to an apparatus controlled with pressurized air and making the pressure difference at a time for decompressing the inside of the dryer larger than the pressure difference at a time for decompressing the inside of the apparatus.

CONSTITUTION: Pressurized air is fed through a pressure feed path 6 by closing a first changeover valve 5 and opening a second changeover valve 7 and fed to the inside of a controlled apparatus 2 via an air dryer 4, the valve 7 and an air communication path 3. At this time, since the inside of the apparatus 2 is raised in pressure after the inside of the dryer 4 is raised in pressure with flow resistance caused by a throttle part 8 of the passage 3, the pressure of the inside of the dryer 4 is made to pressure higher than the prescribed pressure at a point of time when the inside of the apparatus 2 reaches prescribed pressure. At this point of time, in case of closing the valve 7 and opening the valve 5, the high pressure of the inside of the dryer 4 is suddenly decompressed to the atmosphere and an adsorbent incorporated in the dryer 4 is regenerated with pressure swing.