A water soluble cationic polymer applied to a sanitary product. The water soluble cationic polymer comprises a structure having a main chain and a side chain bonded thereto and has a molecular weight of 2 000 or higher. The water soluble cationic polymer is a quaternary ammonium salt homopolymer or a quaternary ammonium salt copolymer. The main chain and side chain of the water soluble cationic polymer bond at one point and the side chain has a quaternary ammonium site. The molecular weight of the quaternary ammonium salt homopolymer is preferably 10 000 000 or less. Alternatively the quaternary ammonium salt copolymer is preferably a copolymer of polymerizable monomers having a quaternary ammonium site cationic polymerizable monomers and anionic polymerizable monomers or nonionic polymerizable monomers and the molecular weight of the quaternary ammonium salt copolymer preferably being 10 000 000 or less.
