There is provided a medical/cosmetic material that retains the properties which are inherent in a polyanionic polysaccharide being a raw material, that has a high level of safety because there is no need to use a chemical crosslinking agent during production, and that makes it possible to place a powder of a water-insoluble polyanionic polysaccharide at an affected area uniformly. The medical/cosmetic material includes a base and a powder dispersed in the base, in which the base contains a water-soluble salt of a first polyanionic polysaccharide, and the powder is formed by water-insolubilizing a powder of a water-soluble salt of a second polyanionic polysaccharide with a treatment liquid containing an acid anhydride.
