We investigated the effect of monoglyceride (MG) addition on qualities of koji. Koji was prepared with MG (0.00-0.20% of rice) addition during rice soaking. We examined cell mass, enzyme activity, and quality evaluation on the basis of the analytical data obtained from the koji . The results were as follows: Cell mass and various enzyme activities of koji were increased by MG addition. Quality evaluation of koji with MG addition was higher than koji without MG. These results suggest that MG addition to the soaking water in the koji preparation process might improve the quality of koji .