The photocatalytic deNOx activities of titania, nitrogen-doped titania, Fe-loaded nitrogen-doped titania, and Pt-loaded nitrogen-doped titania under irradiation from monochrome LED lamps using various light wavelengths were investigated in detail. The improvement of visible light induced photocatalytic activity was successfully realized using Fe and Pt loading. Both Fe-loaded nitrogen-doped titania and Pt-loaded nitrogen-doped titania showed excellent visible light response ability. The photocatalytic activity exhibited by Pt- loaded nitrogen-doped titania was several times higher than that of nitrogen-doped titania under the visible light irradiation of λ = 627 and 530 nm. The relationship between photocatalytic activity and irradiation light wavelength was investigated in detail. The relationship between the intensity of low-level chemiluminescence generated by singlet oxygen (1O 2) and photocatalytic activity was also discussed.