A wafer processing apparatus (14) has a wafer processing vessel (16). A wafer is mounted on a susceptor (22) included in the wafer processing apparatus. Process gases are supplied to the wafer through a shower head (74) disposed in an upper region within the processing vessel to carry out a predetermined process for processing the wafer. The surfaces of aluminum members (16, 74) employed in the wafer processing apparatus are subjected to an organic mechanical chemical polishing process, a blasting process and an aluminum oxide film forming process in that order. It is difficult for unnecessary films to adhere to the thus treated surfaces and it is difficult for unnecessary films deposited on the thus treated surfaces to come off the surfaces. Consequently, intervals between cleaning operations can be extended and production of particles can be suppressed.