The present invention suppresses degradation of an electrolyte film caused by elution of a non-platinum transition metal etc. which forms a core part of a core shell particle contained in a catalyst layer. A membrane electrode assembly comprises an electrolyte film and a pair of electrodes that sandwich the electrolyte film, the pair of electrodes each comprising a catalyst layer and a gas diffusion layer which is disposed on the side of the catalyst layer that is opposite the electrolyte film. At least one of the catalyst layers of the pair of electrodes includes a first catalyst particle and a second catalyst particle. The first catalyst particle is at least one of a platinum particle and a platinum alloy particle. The second catalyst particle is a core shell particle comprising: a core part formed by at least one type of metal selected from a group consisting of non-platinum transition metals; and a shell part covering the core part and formed of at least one of platinum and a platinum alloy. In the catalyst layer of at least one electrode, the proportion of the second catalyst particle is lower on the electrolyte film side than the gas diffusion layer side.
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