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