MEMBRANE ELECTRODE ASSEMBLY AND POLYMER ELECTROLYTE FUEL CELL

To provide a membrane electrode assembly capable of forming a fuel cell excellent in power generation efficiency, and a polymer electrolyte fuel cell.The membrane electrode assembly of the present invention comprises an anode having a catalyst layer containing a proton-conducting polymer and a catalyst, a cathode having a catalyst layer containing a proton-conducting polymer and a catalyst, and a solid polymer electrolyte membrane disposed between the anode and the cathode, wherein the proton-conducting polymer contained in the catalyst layer of at least one of the anode and the cathode, is a polymer (H) having a cyclic ether structural unit and an ion exchange group, and the solid polymer electrolyte membrane contains a fluorinated polymer (S) having an ion exchange group; and the thickness of the solid polymer electrolyte membrane is from 5 to 15 µm, and the ratio of the content M1 [mol%] of the cyclic ether structure unit to the thickness T1 [µm] of the solid polymer electrolyte membrane is 4.5 or more.