Antidiabetic activity of Mori folium ethanol soluble fraction (MFESF) was examined in db/db mice, which is a spontaneously hyperglycemic, hyperinsulinemic and obese animal model . 500 and 1000mg/kg dose for MFFSF (designated by SY 500 and SY 1000, respectively) and 5mg/kg dose for acarbose were administered for 6 weeks. Body weight gain, fasting and non-fasting serum glucose, glycated hemoglobin and triglyceride were all reduced dose dependently when compared between db/db control group and MFESF treated group. At 11th and 13th week after birth, MFESF increased an insulin secretion which may result in lowering serum glucose level. Total activities of sucrase and maltase in SY 500 treated group were decreased when compared to db/db control. On the other hand, those in SY 1000 and acarbose treated groups were increased. This result may suggest that proteins for sucrase and maltase were compensatorily induced due to significant inhibition of glycosidase-catalyzed reaction at doses administered in this study.