To provide a catalyst electrode of low electrical resistance and with the degradation caused by hydrogen peroxide prevented.

In the electrolyte membrane electrode assembly (MEA) with a catalyst layer fitted on the front and the rear surfaces of a solid polymer electrolyte membrane, the catalyst layer is to be structured of an electron conductive substance, a proton conductive substance, and manganese oxide carrying catalyst. The catalyst layer is to have carbon that does not carry catalyst to be added. The iron impurity concentration of the manganese oxide is to be 0.1 ppm or smaller, and a sodium impurity concentration of the manganese oxide, 0.1 ppm or lower.

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