Abstract: In a membrane electrode assembly of the present invention, at least one of a catalyst layer of an oxygen electrode and a catalyst layer of a fuel electrode includes a supported catalyst supporting a metal catalyst containing a platinum group element, a proton conductive polymer electrolyte, and at least one selected from (a) a complex-forming agent having a ligand that forms coordinate bonds with ions of the platinum group element and forms a complex, the ligand containing oxygen as a coordinating atom, (b) a complex of the platinum group element, a ligand of the complex containing oxygen as a coordinating atom, and (c) carbon that has a BET specific surface area of 100 m2/g or greater, satisfies at least one of (i) an R value of Raman spectrum of 0.5 or less and (ii) a lattice spacing d002 between (002) planes of 0.35 nm or less, and does not support the metal catalyst.