Transparent WO3/TiO2 bilayered thin films were deposited on glass substrates by facing target sputtering technique with different amounts of WO3 exposed surface (0%, 30%, 50%, 80%, and 100%) to study the separate role of WO3 and TiO2 in the photocatalytic activity of the composite system. The crystallographic and optical properties of WO3 and the TiO2 layers were investigated in detail. The photocatalytic activity was evaluated by the measurement of decomposition of methanol in gas phase under visible light irradiation with very little ultraviolet content. The rate of decomposition of gaseous methanol largely depends on the ratio of WO3/TiO2 exposed surface. The decomposition efficiency of WO3/TiO2 films increased with an increase in TiO2 exposed surface and the sample with 70% TiO2 exposed area showed the highest efficiency. The surface morphology of all the layers was investigated by the measurement of field emission scanning electron microscope and atomic force microscope. The variation in photocatalytic activity has been tried to be explained on the basis of methanol-photodecomposition mechanism and the intrinsic properties of WO3 and TiO2 semiconductor.