TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred process: The surface treatment of electroconductive support is carried out by activation process, oxidation process by nitric acid, hydrophilization treatment and/or hydroxyl-group addition process. The activation process of electroconductive support is carried out at 500-1200degreesC in gaseous atmosphere containing carbon dioxide, water vapor and/or air. The oxidation process of support is carried out by immersing the support in 0.01 N or more nitric acid at 150degreesC or less. The hydrophilization treatment is carried out by exposing the support to fuming sulfuric acid atmosphere or sulfur trioxide atmosphere, or immersing the support to 0.01 N or more sulfuric acid and irradiating with plasma. The hydroxyl-group addition process of support is carried out by immersing support to an 0.01 N or more alkali solution containing sodium hydroxide, potassium hydroxide or calcium hydroxide at room temperature-150degreesC.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred process: The surface treatment of electroconductive support is carried out by activation process, oxidation process by nitric acid, hydrophilization treatment and/or hydroxyl-group addition process. The activation process of electroconductive support is carried out at 500-1200degreesC in gaseous atmosphere containing carbon dioxide, water vapor and/or air. The oxidation process of support is carried out by immersing the support in 0.01 N or more nitric acid at 150degreesC or less. The hydrophilization treatment is carried out by exposing the support to fuming sulfuric acid atmosphere or sulfur trioxide atmosphere, or immersing the support to 0.01 N or more sulfuric acid and irradiating with plasma. The hydroxyl-group addition process of support is carried out by immersing support to an 0.01 N or more alkali solution containing sodium hydroxide, potassium hydroxide or calcium hydroxide at room temperature-150degreesC.    TECHNOLOGY FOCUS - POLYMERS - Preferred Support: The electroconductive support has specific surface area of 10-100 m2/g, and dibutyl phthalate absorption amount of 100-1000 ml/100 g. A polyelectrolyte is supported in the electroconductive support having higher order structure. The polyelectrolyte is perfluoro sulfonic acid-polytetrafluoroethylene copolymer.