A new diterpene, mp $178{sim}180^{circ}$, $C_{21}H_{28}O_5$, was isolated from the root of Agastache rugosa O. Kuntze in the family of Labiatae. The structure of this compound was postulated as $19(4{ ightarrow}3)-abeo-12,14,15-trihydroxy-11-methoxy-abiet-4(18)$, 8,11,13-tetraen-7-one by spectroscopic methods.