Antidiabetic activity and mechanism of Sangbackpitang (SBPT) was examined in db/db mice, which is a spontaneously hyperglycemic, hyperinsulinemic and obese animal model. SBPT and acarbose were administered orally for 4 weeks. Fasting and non-fasting serum glucose, glycated hemoglobin and triglyceride were all reduced when compared between db/db control group and SBPT treated group. At 12th week after birth, SBPT increased an insulin secretion although statistic significance was not seen. Total activities of sucrase, maltase and lactase in SBPT treated group were all decreased when compared to db/db control. On the other hand, sucrase and maltase activities in acarbose treated groups were increased. Effect of SBPT on mRNA expression of glucose transporter(GLUT-4) was also examined. Quantitation of glucose transporter was performed by RT-PCR and in vitro transcription with co-amplification of rat-action gene as an internal standard. Muscular GLUT-4 mRNA expression in SBPT treated group was increased significantly. These results may suggest that SBPT lowered blood glucose ascribing to inhibition of glycosidase-catalyzed reaction and upregulation of muscular GLUT-4 mRNA expression.