The transparency and uniformity of thin films of titanium oxide (TiO2) are important factors in determining the characteristics of photocatalysts and dye-sensitized solar cells. Synthesized TiO2 nanoparticles were deposited by constant-current electrophoresis deposition in ion-free water and ethanol. The number of cracks was reduced when ethanol was used instead of water. TiO2 nanoparticle thin films produced using a short deposition time had no apparent cracks and a high optical transparency. Moreover, thick TiO2 nanoparticle thin films, which have high optical trans-parency and no apparent cracks, could be deposited by repeating short-time deposition in ethanol.