Our previous study showed that lithium ion conductive glass, Li3PO4-Li2S-SiS2, has high ionic conductivity and high stability against electrochemical oxidation. Such stability will enable solid state batteries to be operated at high voltages. We constructed solid state batteries with LiCoO2 as a positive electrode and indium as a negative electrode material, and investigated their performance. The operation voltage of In/LiCoO2 cell was 3.5 V, which was a high voltage for a solid state battery. The cell showed its high charge-discharge efficiency and good cycling performance, and it was available at high current density (> 500 mu A/cm(2)). Its residual current under charging at constant voltage was extremely small so that it has high overcharge prevention.