The photoelectric properties of the planar bilayer lipid membrane (BLM) of soybean lecithin doped with an amphiphilic azobenzene derivative, 4-octyl-4’-(5-carboxypentamethyleneoxy) azobenzene (8A5), were examined. When a DC voltage is applied across the BLM, the trans-membrane current changes under alternate irradiation with ultraviolet and visible light. A comparative study on the photoresponse of soybean lecithin liposomes doped with 8A5 revealed that the photoelectric properties of the BLM result from the change in the membrane conductivity due to photoisomerization of 8A5.