To provide a composition for introducing a biocidal substance into a fabric in order to provide the treated fabric that has excellent resistance to the removal of the biocidal agent from the fabric by washing.

This invention is a composition that is useful for treating the fabric. The composition contains a silver-containing copolymer having the polymerization units of a monomer X and a monomer Y, wherein the monomer X is an ethylenically unsaturated compound having a substituent group selected from an unsaturated or aromatic heterocyclic ring including at least one of N, O and S atom, and the monomer Y is selected from carboxylic acids, carboxylic salts, carboxylates, organosulfuric acids, organosulfuric acid salts, sulfonic acids, sulfonates, phosphonic acids, phosphonates, vinyl esters, (meth)acrylamides, 8-20C aromatic monomers containing at least one of exocyclic ethylenic unsaturation and combinations thereof.