a method for producing an alloy catalyst for redox reaction comprising alloy particles of platinum and nickel , wherein the alloy particles are equipped at an outer surface with a crystal lattice plane represented by a miller index and have an average particle diameter in a range of 6 to 20 nm , the method comprising : dissolving , in an alcohol , a salt and / or complex of platinum , a salt and / or complex of nickel , and a polymer containing a plurality of salt structures comprising an organic cation and a halogen anion in a polymer chain and heating the resulting solution to reflux under an inert atmosphere .