The ability of InTa1-xVxO4 (x=0, 0.002, 0.005, 0.01) and InTaO4-yNy (y=0, 0.048, 0.059) powders to photocatalyze the oxidative decomposition of gaseous 2-propanol (IPA) when irradiated by the same number of visible or ultraviolet photons was confirmed. The first-principle calculations of InTa0.875V0.125O8 indicated that the V 3d introduced state was discretely situated below the conduction band, which was composed mainly of Ta 5d. Similar calculations of InTaO3.5N0.5 indicated that the N 2p state was above the valence band, which was composed of O 2p. These discrete narrow bands were responsible for the visible light sensitivity in the V- or N-doped InTaO4 compounds.