Provided are an enzyme involved in a glycyrrhizin biosynthetic system, a gene of the enzyme and use thereof in order to stably and continuously provide a large amount of glycyrrhizin. Glucuronosyltransferase with an activity of further transferring glucuronic acid to the hydroxy group at the 2-position of glucuronic acid in an oleanane-type triterpenoid monoglucuronide is identified to provide the transferase, a gene for the transferase and use thereof.