Unique visible-light-responsive TiO2 photocatalysts (lambda > 450 nm) were successfully developed by implantation of V ions into the TiO2 thin films prepared on a quartz substrate by an ionized cluster beam (ICB) deposition method. After V ions implantation into TiO2 thin film, the photocatalytic activity of the thin films for the decomposition of formic acid into CO2 and H2O was found to proceed efficiently under visible light irradiation longer than 450 nm. The TiO2 thin film photocatalysts were characterized by XRD, UV-vis, XPS, FE-SEM and AFM.