The absence of cracks and a high optical transparency are critical factors for obtaining high performance when TiO2 thin films are used as photocatalysts and as the cathode material in dye-sensitized solar cells. Synthesized TiO2 nanoparticles were deposited by constant-current electrophoresis in ethanol. TiO2 nanoparticle thin films deposited at a low current density had no apparent cracks and a high optical transparency. Small TiO2 nanoparticles deposited are thought to be transported at low current densities. This enables TiO2 nanoparticle chains to form by the oriented attachment mechanism and thereby increases the electron diffusion length.