NOVELTY - The electronic-conductivity substance is oxidized, and acidic group is formed on its surface. An ion-exchange complex cation having catalyst is formed on the electronic-conductivity substance using ion contained in the acidic group, and oxidized by oxidizing agent, which provides hydroxyl group to the electronic-conductivity substance. Then, electronic-conductivity substance and aromatic compound having sulfonic acid are dissolved in solvent to obtain catalyst ink, and is laminated on gaseous-diffusion material to obtain catalyst electrode.    USE - Manufacture of catalyst electrode used for polymer electrolyte fuel cell for electric vehicle, mobile telephones, automatic vending machine, underwater robot, submarine, spacecraft and underwater vessel.    ADVANTAGE - The method provides polymer electrolyte fuel cell having improved catalyst efficiency by preventing the aggregation of electronic-conductivity substance.    DETAILED DESCRIPTION - The electronic-conductivity substance is oxidized, and acidic group is formed on the surface of electronic-conductivity substance. An ion-exchange complex cation having catalyst is formed on the electronic-conductivity substance using ion contained in the acidic group to form electronic-conductivity substance having catalyst. Then, the obtained electronic-conductivity substance which supported catalyst is immersed and oxidized by oxidizing agent, which provides hydroxyl group to the electronic-conductivity substance which supported catalyst. An aromatic compound is immersed in sulfonic acid, and heated at 240-260degrees C to form aromatic compound having sulfonic acid group. Then, electronic-conductivity substance and binder are dissolved in solvent to obtain catalyst ink. The catalyst ink is laminated on gaseous-diffusion material to obtain catalyst electrode. The electronic-conductivity substance is a carbon powder. The acidic group is a carbonyl group. The catalyst is platinum and oxidizing agent is ozone-water solution. The aromatic compound comprises anthracene or its derivatives. The sulfonic acid is sulfuric acid, and binder is polyether sulfone. The gaseous-diffusion material is an electroconductive porous base material. The electroconductive porous base material is carbon paper or carbon cloth.