An anodic aluminum oxide film that has uniform and straight nanochannels was exposed to propylene at 800 degreesC, resulting in uniform carbon deposition on the inner-surface of the channels as well as the external surface of the film. The carbon-coated aluminum oxide film was then chemically modified by either fluorination or HNO3 treatment. The change in channel structure due to the carbon deposition and the subsequent chemical modification was analyzed. Gas permeation behavior through these films was examined by using He and N-2. Furthermore, the films were applied to pervaporation separation of water/ethanol mixture and it was found that water preferentially permeated the fluorinated film. The present study demonstrated that even a membrane whose pore size is as large as 24 nm exhibits selectivity in pervaporation.