Photoconductive properties of a mesogenic long-chain tetraphenylporphyrin (C15TPPH2) were investigated for a symmetrical sandwich-type (ITO/C15TPPH2/ITO) cell. The : action spectra and illumination light intensity dependence of the steady state photocurrent indicated that both extrinsic and intrinsic processes of photocarrier generation contribute to the apparent photocurrent behavior which is variant on the mesomorphic phase transitions. In particular, it was inferred that the mesomorphic phase transition from the low- to high-temperature lamellar mesophases leading to the sudden disappearance of photocurrent rectification behavior, depress the extrinsic process of charge carrier generation. These results strongly imply that the photoconductive property of mesogenic materials could be drastically affected by a change of the molecular fluctuation and long-range order through mesomorphic phase transitions.