A useful method was devised for the determination of glucosamine in rice-koji by using High Performance Liquid Cromatography (HPLC). The method was more convenient than colorimetric determinattion usually employed. Glucosamine in the sample and galactosamine added as an internal standard were changed to phenylthiocarbamyl derivatives, which were stable at least for a week, and analyzed by reverse-phase HPLC and detection with absorbance at 254 nm. Results of linearity, reproducibility and recovery test of glucosamine determination showed that this method could be sufficiently applied to estimation of mycelial weight in rice-koji .