CATALYST INK FOR FUEL CELL ELECTRODES, MEMBRANE ELECTRODE ASSEMBLY, FUEL CELL

A catalyst ink used for production of electrodes of a fuel cell includes: catalyst-carrying particles that are particles with a catalyst carried thereon; an ionomer having proton conductivity; and a dispersion solvent in which the catalyst-carrying particles and the ionomer are dispersed. An adsorption amount of the ionomer per unit specific surface area of the catalyst-carrying particles is 0.1 (mg/m 2 ) or greater.