A light-trapping structure with parallel concave cells was developed by using conventional photolithography and electroplating techniques. TiO2 films with a thickness of 50 nm were conformally grown on the surface of the cells by atomic layer deposition (ALD). The linear sweep photovoltammograms revealed that the light-trapping effect is more dominating than the surface area effect on the photoelectrochemical properties of TiO2 films. The light-trapping effect allowed a thin TiO2 film to perform multiple absorptions. By the thinness of TiO2 films, the photogenerated carriers migrated to the surface efficiently and the recombination was controlled. The photocurrent of TiO2 photoanodes was remarkably improved.