ELECTROLYTE MEMBRANE FOR FUEL CELL

PROBLEM TO BE SOLVED: To provide an electrolyte membrane having high proton conductivity and durability.SOLUTION: An electrolyte membrane 10 contains an electrolyte polymer 1 having proton conductivity, and a porous resin membrane 3. The electrolyte membrane 10 has a multilayer structure made of an electrolyte layer 11 which is a layer of the electrolyte polymer 1 and does not include the porous resin membrane 3, and an electrolyte reinforcing layer 12 which is a layer of the electrolyte polymer 1 and includes the porous resin membrane 3. When the thickness percentage in the electrolyte membrane 10, which is the percentage of the thickness of the electrolyte reinforcing layer 12 with respect to the thickness of the electrolyte membrane 10, is higher than 60% and lower than 100%, the density of the porous resin membrane 3 included in the electrolyte reinforcing layer 12 is higher than 250 mg/cmand equal to or lower than 700 mg/cm.