A TiO2 photocatalytic film was prepared by the sol-gel and dip-coating methods. Au-loaded TiO2 photocatalytic films were produced by the photodeposition method. The photocatalytic activity of the films under UV irradiation was evaluated by measuring the degradation of absorbance for a methylene blue (MB) aqueous solution. Au particles deposited on the TiO2 film improved the photocatalytic activity under the O-2 bubbling condition. On the other hand, under N-2 or Ar bubbling, the doubly reduced form of MB, leuco-methylene blue (LMB), was formed at the beginning of UV irradiation, and then both MB and LMB were decomposed gradually by the photocatalytic reaction. In this process, Au particles on the TiO2 film behave as electron traps.