TECHNOLOGY FOCUS - ELECTRONICS - Preferred Components: A membrane electrode assembly of a fuel cell consists of an anode, a cathode, and an electrolytic component provided between the anode and cathode, in which the anode and/or cathode consists of a catalyst layer containing the catalyst and electroconductive particles.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Compound: The metal oxycarbonitride is of formula: NbaMbCxNyOz.a=0.01 or more and less than 1;b=more than 0 and 0.99 or less;x,y=0.01-2;z=0.01-3;a+b=1;andx+y+z=5 or less.Preferred Methods: Alternately, the metal carbonitride is obtained by heat-processing a mixture (b) of oxide of the metal (M), niobium carbide and niobium nitride in an inert gas, heat-processing a mixture (c) of oxide of the metal (M), niobium carbide, niobium nitride and niobium oxide in inert gas, or heat-processing a mixture (d) of a compound containing the metal (M), niobium carbide and niobium nitride in inert gas. Preferred Conditions: The mixtures (a, b, c and d) are heat-processed at 600-1800 degrees C. The metal carbonitride is heat-processed at 400-1400 degrees C. Preferred Property: When the metal oxycarbonitride is measured by a powder X-ray diffractometry (Cu-K alpha -ray), two or more diffraction line peaks are observed between diffraction angle (2( theta )) of 33-43 degrees , and the peak derived from niobium oxide (Nb12O29) is observed. The concentration of oxygen gas and hydrogen gas in the inert gas is 0.1-10 volume% and 5 volume% or less, respectively. EXAMPLE - Niobium oxide(IV) (in g) (4.95), tin oxide(IV) (60 mg) and carbon (1.2) were mixed, pulverized and heat-processed at 1400 degrees C for 3 hours in nitrogen atmosphere, to obtain carbonitride (4.23) containing tin (1 mol%) and niobium. The obtained carbonitride was heat-processed 800 degrees C for 1 hour in an argon atmosphere containing 1 volume% of oxygen gas, to obtain catalyst. The obtained catalyst had excellent durability and high oxygen-reducing ability.