POLYMER ELECTROLYTE MEMBRANE, MEMBRANE ELECTRODE ASSEMBLY AND POLYMER ELECTROLYTE FUEL CELL

To provide a polymer electrolyte membrane capable of producing a polymer electrolyte fuel cell excellent in power generation characteristics and excellent in hydrogen gas utilization efficiency, as well as a membrane electrode assembly and a polymer electrolyte fuel cell obtainable by using it. The polymer electrolyte membrane of the present invention comprises a polymer electrolyte, of which the hydrogen gas permeation coefficient under the conditions of a temperature of 80° C. and a relative humidity of 10% is at most 2.4×10cm·cm/(s·cm·cmHg) and has a membrane thickness of from 7 to 20 μm.