The present invention provides a pentosan polysulfate having an uronic acid content of 7.0-15.0 mass% 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 a pharmaceutically acceptable salt thereof, or a pharmaceutically acceptable solvate thereof, is useful as a pH buffering agent and as an active ingredient of a medicine for the prevention and/or treatment of diseases caused by the abnormal elevation of the function of FGF-2.
