The photocatalytic activities of nitrogen-doped Ta2O5 powders, Ta2O5-Nx (x = 0.10, 0.17, 0.24, 0.35) were evaluated by the decomposition of gaseous 2-propanol (IPA) under visible (Vis) and ultraviolet (UV) light irradiations with the same absorbed photon number (1.4 x 10(14) quanta(.)cm(-2.)sec(-1)). Ta2O5-xNx could decompose IPA under both Vis and UV light irradiations, and its photocatalytic activity depended on the dopant concentration and the wavelength of the irradiated light. The values of photonic efficiency decreased with increasing the degree of x when irradiating with both Vis and UV lights.