Electrolyte membrane for solid polymer type fuel cell and producing method thereof

A method for producing an electrolyte membrane for a polymer electrolyte fuel cell, which comprises forming into a membrane a mixture of a perfluorocarbon polymer having sulfonic acid groups or their precursors and a fluorocarbon polymer which can be fibrillated, laminating a support membrane for stretching to at least one side of the resulting membrane, and stretching the resulting laminated membrane under heating.