This experiment was performed to investigate the effect of Sinjigolpy-tang on the diabetic rats induced by STZ. After experimental diabets was induced by 55mg/kg of STZ injection, we administered Sinjigolpy-tang extract for 14 days after STZ injection. Glucagon and insulin granules in Langerhans islets were stained by use of immunohistochemical(ABC) method and observed the relative amount of the each granules in Langerhans islet by light microscope and image analysis system. Area % of insulin granules in Langerhans islets in Sinjigolpy-tang increased and showed the statistically significant difference with the control group at 14th day. Area % of glucagon granules in Langerhans islets in Sinjigolpy-tang decreased and showed the statistically significant difference with the control group at 7th and 14th day. It can be inferred that Sinjigolpy-tang has a control effect on glucagon and insulin granules in Langerhans islets of diabetic rats induced by STZ.