A gel-type polymer electrolyte, wherein said polymer comprises (A) an ethylene-unsaturated carboxylic acid copolymer or a derivative thereof and (B) a polyalkylene oxide having a hydroxyl group at one terminal thereof or a derivative thereof, which are bonded together by an ester bond. The gel-type polymer electrolyte has a high ionic conductivity, and makes it possible to provides a cell which has excellent charge/discharge characteristics at low temperatures as well as at high temperatures.