The technique of the present invention attains simple and accurate evaluation of the performance of a fuel cell and enables produce of a high-performance electrode catalyst and a high-performance fuel cell. The procedure makes platinum, a noble metal, and iron, a base metal, carried on carbon having a large specific surface area, and heats up the carbon with platinum and iron to a specific temperature to reduce iron. A resulting platinum-iron alloy electrode catalyst exerts excellent catalytic functions. A fuel cell using this electrode catalyst has a high IR compensation voltage. The quantity of carbon monoxide adsorbed by this novel electrode catalyst is not less than 14 Ncc per one gram of platinum. The atomic number ratio of iron (Fe) to platinum (Pt) in the catalyst is not lower than 0.14 by EDX analysis, and the ratio of the binding number of Pt atom with Fe atom to the total binding number relating to Pt atom is not lower than 0.10 by EXAFS analysis. Each electrode catalyst produced is evaluated by measurement of these data. The fuel cell including the electrode catalyst having the favorable result of evaluation ensures the desired performances.