TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Cell: The polymeric electrolyte film has hydrogen-permeation coefficient of less than 3x10-9 cm3.cm/(cm2.s.cmHg) at 80degreesC. The hydrogen-permeation coefficient of the polymer electrolyte film at 80degreesC, is 7 times or less with respect to the hydrogen-permeation coefficient at 23degreesC. The polymeric electrolyte film has hydrogen-permeation coefficient of less than 5x10-10 cm3.cm/(cm2.s.cmHg) at 80degreesC. The oxygen-permeation coefficient of the polymer electrolyte film at 80degreesC, is 10 times or less with respect to the oxygen-permeation coefficient at 23degreesC. The hydrogen-permeation coefficient and oxygen-permeation coefficient of the film at 23degreesC, is less than 5x10-10 cm3.cm/(cm2.s.cmHg) and less than 5x10-11 cm3.cm/(cm2.s.cmHg), respectively. The hydrogen-permeation coefficient and oxygen-permeation coefficient of the film at 80degreesC, is less than 3x10-9 cm3.cm/(cm2.s.cmHg) and less than 5x10-10 cm3.cm/(cm2.s.cmHg), respectively. The polymeric electrolyte film has tensile strength of 0.001-30 MPa at the end of drying process.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Cell: The polymeric electrolyte film has hydrogen-permeation coefficient of less than 3x10-9 cm3.cm/(cm2.s.cmHg) at 80degreesC. The hydrogen-permeation coefficient of the polymer electrolyte film at 80degreesC, is 7 times or less with respect to the hydrogen-permeation coefficient at 23degreesC. The polymeric electrolyte film has hydrogen-permeation coefficient of less than 5x10-10 cm3.cm/(cm2.s.cmHg) at 80degreesC. The oxygen-permeation coefficient of the polymer electrolyte film at 80degreesC, is 10 times or less with respect to the oxygen-permeation coefficient at 23degreesC. The hydrogen-permeation coefficient and oxygen-permeation coefficient of the film at 23degreesC, is less than 5x10-10 cm3.cm/(cm2.s.cmHg) and less than 5x10-11 cm3.cm/(cm2.s.cmHg), respectively. The hydrogen-permeation coefficient and oxygen-permeation coefficient of the film at 80degreesC, is less than 3x10-9 cm3.cm/(cm2.s.cmHg) and less than 5x10-10 cm3.cm/(cm2.s.cmHg), respectively. The polymeric electrolyte film has tensile strength of 0.001-30 MPa at the end of drying process.    TECHNOLOGY FOCUS - POLYMERS - Preferred Compound: The hydrocarbon type-polymer compound is polyphenylene sulfide. The ion exchange capacity of the polymeric electrolyte film is 1-3 meq/g. EXAMPLE - Polyphenylene sulfide film of thickness 25 microns was immersed in a chlorosulfonic acid solution containing 1-chloro butane (in g) (578) and chlorosulfonic acid (8.67), and aged at room temperature for 20 hours. The obtained polyphenylene sulfide film was washed and dried at 23degreesC under 98% RH, 80% RH, 60% RH and 50% RH, respectively for 30 minutes. The obtained polymeric electrolyte film had a thickness of 45 microns and contained polyphenylene sulfide film in which sulfonic acid group was introduced. The obtained polymeric electrolyte film had ion exchange capacity of 1.5 meq/g, proton conductivity of 6x10-2 S/cm and methanol permeability coefficient of 1025 micronsol/cm.square unit. The obtained polymeric electrolyte film had excellent proton conductivity and gas-cut-off property. The electrolyte film provided fuel cell having excellent electric-power-generation characteristic.