Electrolyte membrane for solid polymer fuel cell, method for producing same and membrane electrode assembly for solid polymer fuel cell

Made of a cation exchange membrane made of a polymer having cation exchange groups, it is used as an electrolyte membrane containing cerium ions a polymer electrolyte fuel cell electrolyte membrane. In the case the cation-exchange membrane having sulfonic acid groups, preferably -SO art that cerium ions contained in the cation exchange membrane3- Group and that contains 0.3 to 20%, for example, sulfonic acid groups ion-exchanged with cerium ions. Can be developed at a high energy efficiency, having high power generation performance regardless of the dew point of the feed gas, it is possible to provide stable power generation is also a polymer electrolyte fuel cell as a film over a long period of time.