Provided is a compressor for use in a gas turbine engine, capable of preventing a creation of rust on an inner surface of the compressor casing, without complicating assembling process. The casing 15 of the compressor 3 accommodates rotor and stator blade wheels 13 and 17. The stator blade wheels 17 are supported on the inner surface of the casing 15 through outer flanges 30 thereof. Seal rings 52 are provided at inner surface portions of the casing 15 opposing the radially outward ends of the rotor blade wheels 13. The inner surface of the casing 15 is covered by the seal rings 52 and the outer flanges 30 of the stator blade wheels 17.