Carboxyl group-containing polymer and its composition

To provide a carboxyl group-containing polymer can exert anti-soil redeposition ability with excellent during washing and its composition. And A structural unit derived from an ether bond-containing monomer (A) (a), a sulfonic acid group-containing monomer and (B) from the structural units (b), acrylic acid-based monomer ( a structural unit (c) derived from C) comprises at a specific ratio, the carboxyl group-containing polymer having a specific weight average molecular weight. Further, the carboxyl group-containing polymer, and a specific amount of a compound of structure bisulfite acrylic acid monomer (C) are added, carboxyl group-containing polymer composition. .BACKGROUND