Poly(p-phenylenevinylene) thin film was prepared by spin-casting onto optically transparent ITO conduction glass substrate, and its photoelectric properties were studied with surface photovoltage spectra. A localized subgap electronic transition is found, which causes the photovoltaic response with polarity opposite to that from band-to-band electronic transition (pi-pi*). With the help of the photovoltaic properties under the external electric field, this localized transition is assigned to a electronic transition from the valence band to a local state below the bottom of the conduction band.