TiO2 was electrodeposited into the pores of alumite by alternative electrolysis in (NH4)(2)[TiO(C2O4)(2)] solution (Al/Al2O3/ TiO2), where the alumite was prepared by anodic oxidation of aluminum in phosphoric acid solution. The applied ac voltage to deposit TiO2 was high in the present alumite, compared with that in the case of sulfuric acid solution, because the alumite formed in phosphoric acid solution has a barrier layer thicker than that of the alumite formed in sulfuric acid solution. The particle size of the deposited TiO2 was less than 1 nm. The Al/Al2O3/TiO2 prepared in this study showed high phorocatalytic activity for the decomposition of acetaldehyde.