MEMBRANE ELECTRODE ASSEMBLY AND ELECTROCHEMICAL HYDROGEN PUMP

A membrane electrode assembly includes: an electrolyte membrane that includes a pair of main surfaces; a cathode catalyst layer that is provided to one main surface of the electrolyte membrane; an anode catalyst layer that is provided to the other main surface of the electrolyte membrane; a cathode gas diffusion layer that is provided to the cathode catalyst layer; and an anode gas diffusion layer that is provided to the anode catalyst layer. The anode gas diffusion layer includes a metal steel plate that includes a plurality of vent holes through which gas passes, unevenness is provided to a main surface of the metal steel plate that neighbors the anode catalyst layer, and a difference in a height of the unevenness in a thickness direction of the metal steel plate is less than a thickness of the electrolyte membrane.