The current‐potential characteristics ofn‐TiO2electrodes have been investigated in a photoelectrochemical cell. Photoresponse induced by the light of energy lower than the band gap of TiO2has been observed in the potential range between −1.0 and −1.4 V vs SCE in 1NNaOH. The photoresponse, which is sensitive to the oxygen gas dissolved in solution, has been attributed to some surface states at the TiO2‐electrolyte interface.