Catalysts of the invention are not corroded in acidic electrolytes or at high potential and have excellent durability and high oxygen reducing ability. A catalyst includes a metal oxycarbonitride containing niobium and at least one metal M selected from the group consisting of tin, indium, platinum, tantalum, zirconium, copper, iron, tungsten, chromium, molybdenum, hafnium, titanium, vanadium, cobalt, manganese, cerium, mercury, plutonium, gold, silver, iridium, palladium, yttrium, ruthenium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and nickel. A process for making the catalyst involves a heat treatment.