For the outdoor applications, TiO₂ photocatalyst must respond to solar beam with better efficiency. Surface Modification of a TiO₂ photocatalyst film prepared by sol-gel method was tried to make it responsive to visible light by treating with N₂, H₂, and Ar plasmas. When treated with nitrogen plasma, chemical composition on the surface changed to TiO_2-xN_x. Plasma modified film showed improved optical absorption and photocatalytic activity under the irradiation of visible light. The photocatalytic activity was determined based on the degradation efficiency of methylene blue.