TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The triazole group which has hydrogen on a nitrogen atom is included in principal chain and/or side chain of aromatic polymer. The triazole group is covalently bonded to the principal chain and/or side chain of polymer. The polymer further has an acidic group in a molecule. The content of acidic group is 0.1-5 mmol per 1 g of proton-conductive aromatic polymer. The acidic-group is sulfonic acid group, phosphonic acid group and/or carboxylic acid group. The triazole group exists in organic or inorganic acid compound in ionic-bond state or mixed state. The content of organic or inorganic acid compound is 0.01-20 mmol per triazole group. The triazole group has weight average molecular weight of 5000 or more. Preferred Process: The proton-conductive aromatic polymer film is formed using proton-conductive aromatic polymer. EXAMPLE - 3,3'-bis(sulfo propyloxy)benzidine (in g) (0.921), 3,5-bis(4-amino phenyl)-1H-1,2,4-triazole (0.503), triethylamine (3 ml) and m-cresol (15 ml) were added to a flask, heated at 140 degrees C for 10 minutes under nitrogen stream and stirred, to obtain a transparent homogeneous reaction solution. Then, naphthalene-1,8:4,5-tetracarboxylic dianhydride (1.073), benzoic acid (0.977) and m-cresol (5) were added to the reaction solution. The reaction solution was heated at 175 degrees C for 15 hours, to form a viscous solution. Then, the viscous solution was heated at 195 degrees C under nitrogen stream for 3 hours, and cooled to obtain dark reddish-brown polymer viscous solution. The obtained viscous solution was dripped into acetone (200 ml) and obtained solid was filtered, washed and dried to obtain aromatic high molecular compound in yield of 99% and having ion-exchange capacity of 1.70 meq/g. The obtained high molecular compound (0.1) was dissolved in dimethyl sulfoxide (10 ml), coated on glass plate and dried, to form aromatic high molecular film which was then doped with phosphoric acid. The obtained doped aromatic high molecular film had proton conductivity of 0.01 S/cm and 0.03 S/cm at 80 degrees C and 120 degrees C respectively, excellent hydrolysis resistance and oxidation resistance.