Langmuir-Blodgett films of a cellulose derivative containing porphyrins, porphyrin-cellulose, were fabricated in order to construct a cellulose-based molecular photocurrent generation system. On visible light illumination of the LB monolayer film deposited on an ITO electrode, anodic photocurrents were observed with a quantum yield of 1.6% at an applied potential of 0 V versus SCE, and 3.8-4.6% at 0.2-0.3 V versus SCE. These values indicate that the self-quenching of the photoexcited porphyrins in the cellulose LB film was suppressed, while porphyrin moieties in the LB film had a densely packed structure. This is because the porphyrins are located at a distance of approximately 1.0 nm along the cellulose backbone.