Mori Folium(MF) methanol extract and its water soluble fraction showed significant blood glucose lowering effects alloxan-induced hyperglycemic mice. Their hypoglycemic activities seemed to nothing to do with the stimulation of insulin release or insulin-like action, according to our experiments. On the other hand, MF prevents the hyperglycemic responses from an oral load of starch and glucose in vivo. Since complex carbohydrates present in a diet must be degraded to monosaccharides by $alpha$-glucohydrolase before being absorbed in the gastrointestinal tract, it is thought that blood glucose lowering effects of MF may be related to the inhibition of $alpha$-glucohydrolase catalyzed enzymatic reaction. In addition, experiments that examined an effect of MF water soluble fraction on gastrointestinal movement showed no significant GI movement inhibitory effect. In conclusion, MF water soluble fraction may possess active component which is a potential candidate as an orally active agent for the treatment of diabetes mellitus.