To prepare an ion exchanger resin dispersion capable of giving such an ion-exchange membrane that has a uniform and small thickness so as to be reduced in electrical resistance, has low hydrogen gas permeability, is reduced in dimensional change caused by heating or moistening, exhibits no anisotropy and has high tear strength so as to be excellent in handleability, and is mass- producible.

In this ion exchanger resin dispersion, an ion exchanger polymer having sulfonate groups, preferably a fluorine-containing polymer having the sulfonate groups, and a fibrillar fluorocarbon polymer are dispersed into a dispersion medium. The ion exchanger resin dispersion is obtained, for example, by mixing a fluorine-containing polymer having precursor groups of the sulfonate groups and a fluorocarbon polymer capable of being fibrillated, fibrillating the fluorocarbon polymer capable of being fibrillated, changing the precursor groups of the sulfonate groups into the sulfonate groups, and dispersing the treated mixture into the dispersion medium.