The purpose of the present invention is to provide a method for manufacturing a platinum core-shell catalyst that uses palladium (Pd) as a core metal, or a platinum catalyst containing platinum and a metal besides platinum, wherein the platinum catalyst is supported on carbon and has excellent oxygen reduction activity; and a manufacturing method by which it is possible to manufacture the catalyst industrially on a mass scale. This method for manufacturing a platinum catalyst for a fuel cell containing platinum and a metal besides platinum includes (I) a step for bringing about the presence of a chemical species imparting higher potential than the initial oxide formation potential of the platinum of the platinum catalyst, and (II) a step for bringing about the presence of a chemical species imparting lower potential than the initial oxide formation potential of the platinum of the platinum catalyst, the steps being carried out in a dispersion solution of the platinum catalyst dispersed in an acidic solution containing protons.