A composition contains an inorganic substance obtained as a residue after incinerating skins of marine organisms, and chitin/chitosan. The composition is obtained by incinerating the skins of the marine organisms at a temperature within a range between 600.degree. C. and 1000.degree. C. to obtain the inorganic substance as a residue, obtaining a powdered inorganic substance from the inorganic substance, and kneading the powdered inorganic substance with chitin/chitosan powder.