Thin film n-type TiO2 electrodes of different thickness from 10 to 540 nm were prepared by the sol-gel method so as to investigate the effects of the film thickness on the photocurrent. Since a steep band gradient is expected to form in the thin film TiO2 electrode with thickness less than the space charge layer, such steep band bending would effectively separate the photo-generated electrons and holes, leading to an increase in the photocurrent of the thin TiO2 film electrodes. It was found that in the range of 10-540 nm in thickness, the TiO2 film electrode of 70 nm thick showed a maximum photocurrent, which was approximately six times as large as that of the electrodes of 180-540-nm thickness. This result clearly indicates that the reduction of film thickness is effective for obtaining of the efficient n-type TiO2 film electrode.