Photoelectrochemical reactions on a semiconductor electrode (P-I aSi/ SiOx) with a silver ion conductive solid electrolyte (Ag6I4WO4) have been investigated and photo-sensitizing effect was observed. On the basis of this reaction, photo-battery was examined which had a capability of self-charging under the sun or fluoresence illuminations. The battery consists of two parts. One is a MIS-type photovoltaic part (ITO/P-I aSi/SiOx/Ag), and another is its energy storage part (AgxV2O5/Ag6WO4/AgxV2 O5). Behaviors of photo reactions and the electrochemical charactistics in this system are discussed.