After a solution obtained by extracting protein from cartilages of fishes which are enzyme treated is filtered, alcohol is added to a filtrate to deposit sodium chondroitin sulfate. The sodium chondroitin sulfate manufactured thus can be used for a raw material of medicines, medicine derivatives, medicine additives, cosmetics, and food additives. After a solution obtained by extracting protein which is obtained by enzyme treatment of cartilages of fishes is filtered, the filtrate is dried to manufacture a chondroitin-sulfuric-acid-containing substance. The chondroitin-sulfuric-acid-containing substance manufactured thus is used for, for instance, cosmetics, and food materials.