For the practical use of a polymer electrolyte membrane fuel cell (PEMFC), the structure optimization of the electrode is important in obtaining high performance. Usually, a perfluorosulfonic acid (PFSA) ionomer is used as a binder in the electrode for a novel hydrocarbon electrolyte membrane by many pieces of research because the optimization of hydrocarbon electrode is difficult. However, to reduce costs and the environment load of the F element, the development and the optimization of hydrocarbon electrode for hydrocarbon instead of the PFSA electrode is necessary in the end. This research focused on the adoption of sulfonated poly(arylene ether sulfone) (SPES) as an example of a hydrocarbon ionomer to the electrode and the relationships between the structure of the catalyst layer and the size (radius of gyration) of the SPES related with the molecular weight as a fundamental research for the optimization of the hydrocarbon electrode. From the aspect of the structure of the electrode, we controlled the molecular weight of the SPES in order to enlarge the three-phase boundary for the electrode reaction. We have examined the correlation of the molecular weight of SPES and catalyst utilization, and the structure change of the catalyst layer was observed. The electrode fabricated with low molecular weight SPES showed a high utilization of the catalyst and good fuel cell performance.