Membrane-electrode assemblies are provided having a solid polymer electrolyte membrane that exhibits higher proton conductivity over a wide temperature range, and exhibits superior hot water resistance, chemical stability, toughness and mechanical strength. The membrane-electrode assemblies utilized for solid polymer electrolyte fuel cells include an anode electrode, a cathode electrode and a solid polymer electrolyte membrane, the anode electrode and the cathode electrode disposed on opposite sides of the solid polymer electrolyte membrane. The solid polymer electrolyte membrane contains a polyarylene copolymer with a specific constitutional unit having a fluorine atom and nitrile group introduced in their principal chains.