Diabetes mellitus was induced in male Sprague-Dawley rats weighing 200-245g by injection of streptozotocin(STZ) into the tail vein at a dose of 45mg/kg and were divided into seven groups ; normal, diabetic control, and five experimental groups(fractions of hexane, chloroform(CHCl$_3$), ethylacetate(EtOAc), butanol(BuOH) and water($H_2O$)). The rats of all groups were fed on AIN-93 diet and the five experimental groups were orally administered each fraction for 14 days. The body weight and diet intake were monitored daily. The plasma levels of glucose, insulin, cholesterol, triglyceride, HDL-cholesterol, free fatty acid and aspartate and alanine aminotransferase activities were analyzed. Diabetic rats showed the lower weight gain compared to the normal rats. The plasma glucose levels of the CHCl$_3$, and $H_2O$ fraction groups were significantly lower than the other experimental groups. The plasma insulin level of the CHCl$_3$ fraction group was much higher than that of diabetic control group. The plasma cholesterol levels were increased in all the experimental groups. The groups of hexane, BuOH and H2() fractions showed the lower plasma triglyceride levels compared to diabetic control group. The plasma free fatty acid levels were not significantly different in all groups. HDL-cholesterol levels were definitely higher in hexane, CHCl$_3$ and EtOAc fraction groups than that of diabetic control group. In conclusion, administration of CHCl$_3$ and $H_2O$ fractions of methanol extract of Alisma canaliculatum exhibited hypoglycemic effects in STZ induced diabetic rats, showing the possibility of therapeutic use of Alisma canaliculatum to the diabetes mellitus.