NOVELTY - Diol monomers and dihalide monomers are dissolved in solvent, and heat-dehydrated by contacting with a basic compound, to obtain electrolyte prepolymer solution. Diol monomers and dihalide monomers are added to the obtained solution, to obtain electrolyte polymer fluid. The obtained polymer fluid is separated into solid and liquid, to obtain coating liquid. The obtained coating liquid is cast-coated on base material and evaporated to obtain membranous substance. The obtained membranous substance is contacted with aqueous acid, to obtain polymer electrolyte membrane.    USE - Manufacture of polymer electrolyte membrane used for polymer electrolyte fuel cell. Uses include but are not limited to mobile telephone, personal computer, video camera, digital camera, handheld terminal, digital audio player, domestic electric power supply machine, passenger car, bus and vessel.    ADVANTAGE - The method provides polymer electrolyte membrane having excellent output power generation characteristics, proton conductivity at low humidity condition, mechanical strength, workability, hydrolysis resistance and durability.    DETAILED DESCRIPTION - Diol monomers and dihalide monomers containing 20-100 mol% of diol monomers which have hydrolyzable group are dissolved in solvent, such that total content of the diol monomer which has ionic group, and the dihalide monomer which has ionic group is 0-20 mol%, and heat-dehydrated by contacting with a basic compound, to obtain electrolyte prepolymer solution. Diol monomers containing 10 mol% or more of diol monomers which have ionic group, and dihalide monomers containing 20-100 mol% of dihalide monomers which have ionic group are added to the obtained electrolyte prepolymer solution, such that total content of the diol monomer which has an ionic group, and the dihalide monomer which has an ionic group is +10 to 100 mol% of total content of the diol monomer which has an ionic group and the dihalide monomer which has an ionic group, to obtain electrolyte polymer fluid. The obtained electrolyte polymer fluid is separated into solid and liquid by centrifuged method, to obtain coating liquid. The obtained coating liquid is cast-coated on base material and evaporated by heating solvent to obtain membranous substance. The obtained membranous substance precursor is contacted with aqueous acid, to obtain polymer electrolyte membrane.