For the purpose of obtaining oxide thin films with high photocatalytic activity, we have successfully prepared the TiO2 anatase polycrystalline films with a two-dimensional spinodal phase-separated structure (2D-SPSS) in micron size by the sol-gel dip-coating method from a titanium tetraisopropoxide solution containing polyoxyethylene(20) nonylphenyl ether. It has been also found that TiO2 films with a variety of morphologies in addition to the 2D-SPSS can be formed by controlling the molar ratio of water to titanium tetraisopropoxide. The methylene blue photodegradation activity of the 2D-SPSS TiO2 film was higher than that of dense TiO2 film prepared from a TiO2 sol without co-existing polymer. This fact can be interpreted in terms of possessing a high specific surface area available for the photocatalytic reaction. (C) 2004 Elsevier Ltd. All rights reserved.