In a membrane electrode assembly (113), a cathode catalyst layer (109) includes a catalyst, an electrically conductive support that supports the catalyst, and an ionomer having a proton conductivity. The cathode catalyst layer (109) includes an inner portion that is in contact with an electrolyte membrane (102) and an outer portion that is in contact with or is opposite to the cathode gas diffusion layer (110). When a ratio of a mass of the ionomer to a mass of the support is defined as an ionomer presence ratio, the ionomer presence ratio in the inner portion is lower than the ionomer presence ratio in the outer portion. The state of coverage of the support with the ionomer in the inner portion is different from the state of coverage of the support with the ionomer in the outer portion.