Sodium alginate preparation (average of m.w.>300, 000) was depolymerized by incubation with Vibrio alginolyticus SUN53 (NITS-P-1.4) isolated from marine bacteria in sandy beach of Nagasaki by Ueda. The lyophilized powder of depolymerized product of sodium alginate, of which molecular weight was approximately 1, 000, was obtained. The solution of the product inhibited the activities of sucrase, maltase, isomaltase, lactase, and trehalase using rat intestinal brush border membrane vesicles. By the addition of the depolymerized sodium alginate, sucrase and lactase, maltase, and isomaltase were inhibited approximately 60%, 35%, and 45%, respectively. These inhibitory effects depended on the concentration of the product. However, trehalase was not so clearly inhibited. These inhibitory modes were competitive by Lineweaver-Burk plot. These results suggest that the depolymelized sodium alginate by Vibrio alginolyticus SUN53 could contribute to develop the ingredient, which have the possibility of the suppressive effect of postprandial blood glucose levels.