A polymer electrolyte providing lithium secondary batteries in which growth of lithium dendrites is suppressed and batteries exhibiting excellent discharge characteristics in low to high temperature, comprising a polymer gel holding a nonaqueous solvent containing an electrolyte, wherein the polymer gel comprises (I) a unit derived from at least one monomer having one copolymerizable vinyl group and (II) a unit derived from at least one compound selected from the group consisting of (II-a) a compound having two acryloyl groups and a (poly)oxyethylene group, (II-b) a compound having one acryloyl group and a (poly)oxyethylene group, and (II-c) a glycidyl ether compound, particularly the polymer gel comprises monomer (I), compound (II-a), and a copolymerizable plasticizing compound.