TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: Alternatively, the magnetic particles-supported catalyst contain electroconductive particles, catalyst particles supported by the electroconductive particles, and magnetic particles supported by the electroconductive particles. Preferred Particles: The catalyst particles are magnetic-alloy particles. The catalyst particles and magnetic particles are oxide particles of iron, cobalt, nickel, zinc, manganese and/or copper. The magnetic-alloy particles contain platinum, cobalt, and nickel, iron, titanium, copper, manganese, aluminum, ruthenium, tungsten and/or molybdenum. Preferred Properties: The content of platinum and cobalt contained in the magnetic-alloy particles is 40-98 weight% and 2-60 weight%, respectively. The content of catalyst particles contained with respect to total content of the magnetic particles-supported catalyst is 5-50 weight%. The oxide particles have a spinel structure or perovskite structure. The weight ratio of catalyst particles and magnetic particles is 40:60-90:10. The particle diameter of catalyst particles and magnetic particles is 1-10 nm and 1-10 nm, respectively. Preferred Methods: Alternatively, the magnetic particles-supported catalyst is formed by forming electroconductive particles-supported catalyst metal component (a), forming electroconductive particles-supported catalyst particles by heating catalyst the metal component (a) at 250-600 degrees C in non-oxidizing atmosphere, adding a magnetic precursor, heating, and magnetically-polarizing by applying magnetic filed. EXAMPLE - Chloroplatinic-acid hexahydrate (in g) (4.5) and cobalt-nitrate hexahydrate (2.5) were dissolved in mixture of water (80 ml) and ethanol (20 ml). Then, citric acid (2.2) was added, to obtain aqueous solution containing citric-acid complex ion of platinum and cobalt. The obtained citric-acid complex ion aqueous solution (2 ml) was impregnated into carbon black having average particle diameter of 30 nm, mixed, and dried at 90 degrees C. The impregnation process was carried out repeatedly, dried at 90 degrees C for 10 hours, and heat-processed at 550 degrees C for 4 hours under argon gas. Then, reduction process was performed for 2 hours, to obtain carbon particles-supported platinum-cobalt catalyst.