CATALYST LAYER FOR FUEL CELL

There is provided a catalyst layer for a fuel cell that can inhibit reduction in water electrolysis function. The catalyst layer for a fuel cell according to this disclosure comprises carbon supports on which Pt particles are supported, and Ir oxide particles, wherein the ratio of the mean primary particle size of the Ir oxide particles with respect to the mean primary particle size of the Pt particles is 20 or greater. The mean primary particle size of the Pt particles may be 20.0 nm or smaller and the mean primary particle size of the Ir oxide particles may be 100.0 nm to 500.0 nm.