It is an object of the present invention to provide a cathode catalyst for fuel cells containing platinum and iron which can maintain the durability of a battery and can make a battery high output. The cathode catalyst for fuel cells comprises a supporting layer which consists of an alloy containing platinum and iron and further containing the third component which has an affinity for iron including one or more sorts of elements selected from the group consisting of tungsten, titanium, molybdenum, rhenium, zinc, manganese, tin, tantalum and rhodium, and a support on which the supporting layer is loaded. A catalyst using an alloy containing platinum and iron enables the batteries to become high output. By alloying one or more sorts of elements of the third component which has an affinity for iron with an alloy containing platinum and iron, it is possible to prevent eluting of the iron into the electrolyte.