Abstract: A method and apparatus for cooling compressed air include the following. Compressed air is introduced into a vortex tube where cold air and warm air are generated. The cold air and warm air are introduced into a pressure vessel where the temperature and moisture of the compressed air are adjusted. The adjusted compressed air is fed to a downstream side of the pressure vessel. Before the generated cold air and warm air are introduced into the pressure vessel, the warm air is introduced into a pre-pressure vessel disposed at an upstream side of the pressure vessel. The cold air is introduced into a cooling tube or cooling chamber which is disposed inside the pre-pressure vessel which is disposed at the upstream side of the pressure vessel. The warm air is adjusted by cooling. The adjusted warm air is introduced into the pressure vessel from the pre-pressure vessel together with the cold air.