A polymer electrolyte is formed by curing a composition prepared by mixing a polymer of compounds of polyethylene glycol di(meth)acrylates and/or multi-functional ethyleneoxides; one selected from a vinylacetate monomer, a (meth)acryalte monomer, and a mixture of a vinylacetate monomer and a (meth)acrylate monomer; and an electrolytic solution containing a lithium salt and an organic solvent.