The photovoltaic effect has been observed for a titanium dioxide (TiO2) and zinc phthalocyanine (ZnPc) composite cell which is denoted as ITO/TiO2/ZnPc/Au. The photocurrent flows from the ZnPc layer to the TiO2 layer in the external circuit when the cell is illuminated, and the photocurrent and photovoltage of the cell are directly and logarithmically proportional to the light intensity, respectively. A clear rectifying effect is observed in their current-voltage relationships. Not only the photovoltaic effect in the cell but also photoconduction in the TiO2 layer is observed under ultraviolet light illumination. The wavelength dependence of the photocurrent reveals that the collection efficiency of the cell at any wavelength is determined mainly by optical absorption in the ZnPc layer. This result also shows that the major part of incident light in the visible region effectively contributes to photocarrier generation because of the wide band gap of TiO2. and the excited ZnPc molecules play an important role in the photovoltaic effect.