To provide an apparatus for making dry compressed air, which is flexible in application and easy to carry.

The apparatus for making dry compressed air comprises a refrigeration type air dryer 12, filters 30 and 40 for removing dust, oil mist and odor, a membrane type air dryer 50 and other various instruments 20, in all of which drain water can be produced from the compressed air, and further comprises an oil-water separation device 60 for removing foreign matter contained in the resulting drain water. A single set of the filters 30 and 40 or a plurality of sets of the filters 30 and 40 installed continuously are integrated with the membrane type air dryer 50 to constitute an integrated unit 250.