This study examined the anti-diabetic effect of a silkworm extract in C57BL/6J mice, an ob/㏈ model, fed a high fat diet for 8 weeks. The body weight was not significantly different with the silkworm-extract supplement, nor did food intake and body weight gains also did not differ significantly among the high-fat diet groups. However, the water intake by the silkworm-extract supplemented groups increased significantly compared with that by the distilled-water supplement group, nonetheless, the FER did not differ significantly. For all groups, the blood glucose increased the most after 30 minutes and yet returned to a fasting level within 90 minutes. The fasting time and resulting glucose tolerance for the silkworm-extract supplemented groups were significantly decreased compared to that for the high fat diet with distilled water supplement group, while the level of blood glucose in silkworm-extract supplemented groups was significantly decreased compared with than in the diabetic control group. The HbA1c and insulin levels were no different among the groups. The sucrase and lactase activities in the proximal small intestine were significantly decreased in the silkworm-extract supplement groups compared to that in the diabetic control group. There was no significant difference in the glycogen contents in the liver and muscle among the groups. In conclusion, it was found that the silkworm-extract supplement repressed the disaccharidase activity in the small intestines mucosa of the C57BL/6J mice.