A TiO2 film was deposited onto alumite using an electrochemical technique, where the initial electrodeposition was carried out by ac electrolysis in (NH4)(2)[TiO(C2O4)(2)] solution, followed by pulse electrolysis in TiCl3. This is a new method to prepare a mesoporous TiO2 photocatalyst film consisting of nanosized particles and to directly fix them onto the alumite substrate (Al/Al2O3). The sizes of the TiO2 particles in the prepared film were about 5 nm, and they consisted of mixtures of the anatase, rutile, and amorphous phases. This film had a high catalytic activity for the decomposition of acetaldehyde even under fluorescent lamp illumination. Moreover, the preparation cost is very low compared with other methods. Therefore, the prepared Al/Al2O3/TiO2 plate is very useful for the practical photodecomposition of chemical contaminants in the atmosphere. The mechanisms of the TiO2 deposition and the photocatalysis are discussed.