The present invention provides a novel sulfated polysaccharide having an anticoagulant activity. Specifically, the present invention provides the polysaccharide comprising a repetitive structure of a disaccharide unit composed of a hexuronic acid (HexA) residue and a α-D-glucosamine (GlcN) residue and having 13% or higher of a 3-O-sulfation rate in GlcN residues.