Highly nitrogen-substituted TiO2 (N-TiO2) thin film photocatalysts were prepared by a radio-frequency magnetron sputtering (RF-MS) deposition method. N-TiO2 thin films with low nitrogen concentration (0.5%) exhibited a small absorption band as a shoulder in the 400-500 nm wavelength region, indicating that isolated N 2p orbitals are formed above the O 2p orbitals. However, N-TiO2 with higher nitrogen concentration (6%) exhibited a sharp absorption edge at 500 nm, indicating that visible light absorption is due to a band gap transition. These N-TiO2 thin films could operate as photocatalysts to decompose 2-propanol diluted in water under visible light. The band structure of N-TiO2 was also determined by photoelectrochemical measurements and H2 and O2 evolution was carried out from an aqueous solution involving sacrificial reagents.