Microbial transformation of (-)kaur-l6-en-19-oic acid and (-)pimara-9(1l), 15-dien-19-oic acid from A. koreanum was investigated. Throughout the screening of the capability of metabolizing these bioactive diterpenoids, two microorganisms have chosen among various fungi and streptomycetes tested. Scale-up fermentation with Fusarium oxysporum KCTC 6051 produced two metabolites related to the precursor diterpenoids. The two metabolites were isolated by column chromatography and identified by chemical and spectroscopic methods as $2eta$, $16alpha$-dihydroxy kauran-19-oic acid and $16alpha$-hydroxy kauran-19-oic acid. However any microorganisms capable to transform (-) pimara-9(11), 15-dien-19-oic acid was not screened in this condition.