NOVELTY - The membrane electrode assembly (10) has oxygen electrode (1) containing catalyst layer (1b), fuel electrode (2) containing catalyst layer (2b) and solid polymer electrolyte membrane (3) arranged between the electrodes. The catalyst layer contains complex forming agent (a) having ligand which coordinates with the ion of platinum group element and forms a complex, complex (b) of platinum group element and carbon (c) with BET specific surface area of 100 m2/g or more. The complexes have ligand containing oxygen as coordinating atom.    USE - Membrane electrode assembly is used in polymer electrolyte fuel cell (claimed) used as electric power generation device for motor vehicles, and as portable power supply.    ADVANTAGE - The membrane electrode assembly has high durability and provides fuel cells with improved high electric power generation performance.    DETAILED DESCRIPTION - The membrane electrode assembly has oxygen electrode containing catalyst layer which reduces oxygen, fuel electrode containing catalyst layer which oxidizes the fuel and solid polymer electrolyte membrane arranged between the electrodes. The catalyst layer contains a support comprising catalytic metal doped with platinum group element and proton conductive polymer electrolyte. The catalyst layer contains complex forming agent (a) having ligand which coordinates with the ion of platinum group element and forms a complex, complex (b) of platinum group element and carbon (c) with BET specific surface area of 100 m2/g or more, R-value of 0.5 or less in Raman spectrum and (002) face plane spacing d002 of 0.35 nm or less. The carbon is not supported with the catalyst metal. The complexes have ligand containing oxygen as coordinating atom. The complex forming agent is a compound having carbonyl group or phosphoryl group, preferably acetyl acetone or its derivative(s), citric acid, acetyl tributyl citrate, ammonium citrate, ethylenediamine tetraacetic acid, nitrilotriacetic acid, hydroxyethyl imino triacetic acid, hydroxyethyl ethylenediamine triacetic acid, diethylenetriamine penta-acetic acid, triethylenetetraamine sexa-acetic acid, 1,3-propanediamine tetraacetic acid, 1,3-diamino-2-hydroxypropane tetraacetic acid, glycine, dihydroxyethyl glycine, hydroxyethylidene diphosphonic acid, nitrilo trismethylene phosphonic acid, phosphonobutane tricarboxylic acid or N,N,N',N'-tetrakis(phosphonomethyl)ethylenediamine.    DESCRIPTION OF DRAWING(S) - The drawing shows the sectional view of the polymer electrolyte fuel cell membrane electrode assembly.    Oxygen electrode (1)    Catalyst layers (1b,2b)    Fuel electrode (2)    Solid polymer electrolyte membrane (3)    Membrane electrode assembly (10)    Polymer electrolyte fuel cell (11)