The present invention provides pentosan polysulfate having a weight average molecular weight of 5000 or less and a content of acetyl groups of 0% to 2.0% by mass, or a pharmaceutically acceptable salt thereof, or a pharmaceutically acceptable solvate thereof. The pentosan polysulfate of the present invention, or a pharmaceutically acceptable salt thereof, or a pharmaceutically acceptable solvate thereof exhibits an anti-Xa activity and an anti-Xa/anti-IIa activity ratio, which are suitable for practical use, and is useful as a pharmaceutical composition such as an anticoagulant.
