A method for evaluating the quality of koji from various analytical data was proposed. Koji was digested in a solution containing acetate buffer, pH 5.0, at 55°C for 5 hr, and the filtrate of digestswas analyzed for specific gravity (Bé degree), glucose and amino acids. Moisture content (KM) of koji was also determined. From these results, true digestion value (SS), true saccharification value (ST), total potency (TR=SS×ST), true amino acidity (S A), saccharification ratio (1/SS), amino acid ratio (SA/TR), and true glucose (SG) were calculated by equations respectively defined. When values of koji for highly ranked sake ( ginjo-koji ) and for common sake were compared during the process of koji making, changes in measured values other than SA were smaller for the former koji than for the latter at the time of shimai-shigoto (2 nd mixing operation) and thereafter. When properties of koji were plotted in a 3-axle radar chart prepared from axles of TR, SA/TR, and ST/TR, koji for highly ranked sake showed lower TR and higher SA/TR than koji for common sake. A 5-axle radar chart prepared from axles of SS, ST, SA, KM and SG showed that koji for highly ranked sake gave almost regular pentagonal shapes, while koji for lowly ranked sake gave irregular pentagonal shapes having high KM and SG.