The 6-O-phthalocyanine cellulose derivative, 2,3-di-O-myristyl-6-O-[p-(9(10),16(17),23(24)-tri-tert-butyl-2-zinc(II)phthalocyaninyl-benzoyl)cellulose (8e) was synthesized in a high yield with the degree of substitution of 0.33 for the phthalocyaninyl group (DSphthalocyanine) via the esterification of 2,3-di-O-myristyl cellulose (1) with the mono-substituted phthalocyanine derivative ([9(10),16(17),23(24)-tri-tert-butyl-2-[4-(carboxy)phenoxy]phthalocyaninato]zinc(II), 7). A chloroform solution of compound 8e was more stable under illumination than that of low molecular weight phthalocyanine, [2(3),9(10),16(17),23(24)-tetrakis(tert-butyl)phthalocyaninato]zinc(II). Langmuir-Blodgett (LB) monolayer films of compound 8e were prepared on a variety of different substrates using the vertical dipping method with an annealing time of 5 min. An LB monolayer film of compound 8e on an indium tin oxide (ITO) electrode exhibited a photocurrent generation performance in the range of 600-700 nm. The photocurrent density of the film composed of 8e at 680 nm was better than that of 2,3-di-O-myristyl-6-O-(zinc(II) phthalocyaninyl) cellulose (3) which was the corresponding phthalocyanine-containing cellulose synthesized through a phthalocyanine-ring forming reaction on the cellulose backbone according to an existing procedure.