Providing a visually observable material for medical treatment, which is preferable as an adhesion preventive material and a hemostatic material for biological organisms. A material for medical treatment comprising a crosslinking composition comprising at least two components of a crosslinking polysaccharide derivative with an active ester group reactive with active hydrogen in the co-presence of an alkali, where the active ester group is preliminarily introduced in a side chain of a polysaccharide and the crosslinking polysaccharide derivative is not yet crosslinked, and a carbonate including at least one type of carbonate generating divalent carbonate ion in an amount at a mass ratio of 0.03 or more to the polysaccharide derivative.
