Aspergillus oryzae No.10 (Higuchi) was cultivated for 30-72 hours at 30℃ in a synthetic medium by surface or shaking culture, and the lipoic acid content of the mycelium was measured by microbioassay method using Streptococcus faecalis 10Cl. No significant difference was observed between the lipoic acid contents of the mycelia obtained by the two different methods of culture. The maximum value, 1μg/g which was almost equal to the contents of yeast or liver was obtained in 72 hours cultivation.