A nitrogen-doped titanium oxide nanoparticle was synthesized via simple sol-gel route and N-doped TiO₂ film was prepared to investigate the photocatalytic properties of the nanoparticle. In order to obtain N-doped anatase nanoparticle crystalline, NH₄OH solution was added dropwise to titanium tetraisopropoxide (TTIP) solution at 80^oC and the particulate sol was reacted for 24 hours. The synthesized white powder leads to pale yellowish powder by following heat-treatment process at 450^oC in air for an hour. X-ray photoelectron spectrum and UV-vis spectrum were analyzed to confirm that the nitrogen was doped into TiO₂ nanoparticle successfully. The visible light-induced photocatalysis and hydrophilicity of the N-doped TiO₂ film were enhanced significantly as compared with undoped one. The improved photo activity was attributed to extended absorption range of the TiO₂ nanoparticle from ultraviolet to visible wavelength.