The proteolytic enzyme extracted from Neungee [Sarcodon aspratus (Berk.) S. Ito] was purified by using Tris-acryl CM-cellulose column chromatography and chromatofocusing. The specific activity of the purified enzyme increased 15.8 times as compared with that of the crude enzyme. The enzyme was homogeneous on polyacrylamide gel electrophoresis and stable at pH values ranging from 4.0 to 10.8. The enzyme activity remained unchanged when the mushroom and the purified enzyme were stored for 3 years and 6 months at 4°C, respectively. The enzyme was found to be an endogeneous protease.