A method of manufacturing an electrolyte membrane for fuel cells with improved durability for fuel cells includes: preparing a substrate; applying a first ionomer solution onto the substrate; inserting a porous support into the first ionomer solution to impregnate the first ionomer solution in the porous support; allowing the first ionomer solution-impregnated porous support to stand; applying a second ionomer solution to the first ionomer solution-impregnated porous support; and drying the porous support.