NOVELTY - The polymer electrolyte secondary cell has anode, cathode, polymer electrolyte containing non-aqueous solvent, polymer and lithium salt, and cell case (3) for accommodating electrodes and polymer electrolyte. The non-aqueous solvent contains ethylene carbonate and/or propylene carbonate. The volume ratio of ethylene carbonate and propylene carbonate in the non-aqueous solvent, is 60% or more at 25degrees C and 1 atmosphere. The polymer comprises copolymer having monomer containing N,N-dimethyl acrylamide and a compound with 3 or more acrylate groups and/or methacrylate groups.    USE - Polymer electrolyte secondary cell used as power source of mobile appliances.    ADVANTAGE - The polymer electrolyte has superior performance for holding electrolytic solution, conductivity and security during cell overcharge. The polymer electrolyte secondary cell eliminates the possibility of solution leakage and has superior discharge characteristics and improved safety during overcharge.    DETAILED DESCRIPTION - The polymer electrolyte secondary cell has anode, cathode, polymer electrolyte containing non-aqueous solvent, polymer and lithium salt, and cell case for accommodating electrodes and polymer electrolyte. The non-aqueous solvent contains ethylene carbonate and/or propylene carbonate. The volume ratio of ethylene carbonate and propylene carbonate in the non-aqueous solvent, is 60% or more at 25degrees C and 1 atmosphere. The polymer comprises copolymer having monomer containing N,N-dimethyl acrylamide and a compound with 3 or more acrylate groups and/or methacrylate groups. The ratio of compound with respect to total mass of monomer is 10-30 mass%. The ratio of polymer with respect to the polymer electrolyte is 1-2 mass%. The polymer electrolyte further contains succinic anhydride. The polymer is formed by polymerization of a monomer in the cell. The cell case is made of aluminum laminate film. The monomer further contains tertiary vinyl carboxylate, such as vinyl pivalate.    DESCRIPTION OF DRAWING(S) - The drawing shows frontal perspective view of cell with a film cell case.    Electrode assembly (1)    Film cell case (3)    Sealed portions (4a-4c)    Anode lead (7)    Cathode lead (8)