This invention is intended to improve the coverage of a platinum or platinum alloy surface with gold when producing a catalyst comprising carrier particles that support gold-modified platinum or platinum alloys. The invention provides a method for producing a catalyst comprising carrier particles that support gold-modified platinum or platinum alloys comprising a step of gold reduction comprising adding carrier particles that support platinum or platinum alloys, a reducing agent, and a gold precursor to a liquid medium and mixing the same, wherein the reducing agent is added to adjust the ORP value (i.e., an oxidation-reduction potential with reference to the silver-silver chloride electrode) of the liquid medium to −630 to +230 mV upon completion of addition.