Gold-platinum black layer was electrochemically deposited on a platinum electrode in the mixed solution of tetrachloroaurate, hexachloroplatinate, and lead acetate. The surface of the electrode after the deposition was characterized by scanning electron microscopy, X-ray microanalysis, and cyclic voltammetry. There was no evidence of the localization of gold and platinum, and the deposition ratio of gold and platinum was proportional to the concentration of tetrachloroaurate and hexachloroplatinate.