A photocatalytic membrane reactor, in which permeation of solutes through a membrane and a photocatalytic reaction occur simultaneously, that is, a photocatalytic membrane reactor, is described. Using trichloroethylene (TCE), a decomposition ratio in excess of 95% in the permeate stream to that in the feed stream was achieved by means of porous titanium oxide (TiO2) membranes, when approximately I ppm TCE solution was fed to the TiO2 membranes under irradiation by a blacklight. The decomposition ratio, defined as the concentration ratio of the permeate to the feed stream, decreased with applied pressure and the feed concentration. A proposed photocatalytic reaction model where a photocatalytic reaction in the outer reaction zone and in the inner reaction zone under membrane permeation conditions is consistent with the observed experimental data.