Abstract: A compression apparatus including an electrolyte membrane; an anode catalyst layer in contact with one of main surfaces; a cathode catalyst layer in contact with the other of the main surfaces; an anode gas diffusion layer in contact with the anode catalyst layer; and a cathode gas diffusion layer in contact with the cathode catalyst layer, the membrane electrode assembly used in a compression apparatus that generates compressed hydrogen by applying voltage between the anode catalyst layer and the cathode catalyst layer to move protons, taken out of an anode fluid supplied to the anode catalyst layer, to the cathode catalyst layer via the electrolyte membrane. The cathode gas diffusion layer includes a porous carbon sheet and a porosity of a first surface layer in an opposite side to a side of the cathode catalyst layer is lower than a porosity of a layer inward from the first surface layer.