TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The polyamide sulfamidic acid is of formula -(-N(H)-C(=O)-Ar1(CONHSO3H)2-C(=O)-N(H)-Ar2-)n-.Ar1,Ar2=aromatic ring or group containing an aromatic ring;n=average degree of polymerization and is 100-300000.Preferred Material: The polyamide sulfamidic acid is a sulfamidation product of carboxylic acid groups in side chains of polyamide acid.Preferred Method: The polyamide sulfamidic acid is obtained by subjecting the carboxylic acid groups in side chains of the polyamide acid to an acid chlorination reaction, reacting the product with amidosulfuric acid triethylamine salt, and then, subjecting that product to a cation exchange reaction. EXAMPLE - Polyamide sulfamidic acid was prepared according to scheme (1) using polyamide acid (3) where Ar1 and Ar2 are both benzene. Next, 0.60 g of thionyl chloride was slowly dripped into a solution of 0.21 g of polyamide acid in 200 mL of N,N'-dimethyl acetamide under a nitrogen atmosphere and mixed for 3 hours with stirring. The resulting solution was concentrated to 20 mL and poured into 400 mL of dichloromethane. The formed precipitates were filtered and washed with dichloromethane, and then dissolved in 20 mL of N,N'-dimethyl acetamide. Separately, 0.49 g amidosulfuric acid and 0.51 g triethylamine were added to 3 mL of dichloromethane to form amidosulfuric acid triethylamine salt. The formed salt was slowly dripped into the above polymer solution under a nitrogen atmosphere and mixed for 3 hours with stirring. The resulting solution was poured into 400 mL of dichloromethane. The formed precipitates were filtered and washed with dichloromethane, and then dried at 50degreesC overnight under reduced pressure. As a result, 0.32 g of yellow powder was obtained for a yield of 81%. In addition, an absorption resulting from a carbonyl group of 1685, 1654 cm-1 and an absorption resulting from a sulfonic acid group of 1118, 1045 cm-1 were observed in infrared spectrums of the yellow powder. Thus, it was confirmed that polyamide sulfamidic acid triethylamine salt was formed. Next, a solution of N,N'-dimethyl acetamide containing 0.27 g of the previously prepared polyamide sulfamidic acid triethylamine salt was passed through a cation exchange resin to exchange protons. The obtained solution was concentrated to 20 mL and dripped into 400 mL of dichloromethane. The formed precipitates were filtered and washed with dichloromethane, and then dried at 50degreesC overnight under reduced pressure. As a result, 0.19 g of light yellow powder (polyamide sulfamidic acid) was obtained for a yield of 95%. Carbon powders supporting 50% by mass of platinum were added to a solution of the above polyamide sulfamidic acid in N,N'-dimethyl acetamide in a mass ratio of carbon powder supporting platinum to the polymer of 2:1. This mixture was then stirred to obtain a suspension. The obtained suspension was applied to a porous carbon body with a porosity of 75% using a die coater. The porous carbon body had a porous carbon layer. Then, the porous carbon body was dried to form a porous electrode useful for a fuel cell. The polyamide sulfamidic acid membrane prepared previously was interposed between a pair of porous electrodes to form a single fuel cell. Wet hydrogen as a fuel and a wet air as an oxidant were supplied to the fuel cell and electricity generation was tested at 80degreesC. A voltage of 0.65 V was generated at an open circuit voltage of 0.95 V and a current density of 200 mA/cm2 confirming that the fuel cell exhibited excellent operating capabilities.