This study was performed to investigate the antidiabetic effects of leaves and stems in the Dendropanax morifera Leveille (DML) hot Water extracts and ethanol extracts in the diabetic rats. Diabetic experimental model was established by intraperitoneal injection of streptozoticin (STZ) into male ICR mice. DML hot Water and ethnol extracts were concentration of 100 mg/kg and 200 mg/kg were administered orally in diabetic rats. Body weight, blood glucose levels were recorded for 14 days and serum insulin levels and urinalysis and histopathological observation of pancreatic islets were measured at the day 14. oral administration of DML extracts reduced significantly body weight in DW-200 groups. The blood level of glucose was decreased in the dose-dependent manner than DC group; 37.3% in the STZ+DW-200 group, 37.3% in the STZ+DE-200 group, 32.4% in the STZ+DW-100 group, and 19.3% in the DE-100 group. The serum level of insulin was improved 1.9 folds in the STZ+DW-200 group and 2.3 folds in the STZ+DE-200 group compared to the DC group. The urine level of glucose was improved 3.8 folds in the STZ+DW-200 group and 11.4 folds in the STZ+DE-200 group compared to the DC group. Immunohistochemical stainig for insulin clearly showed that pretreatment with DW-200 group and DE-200 group blocked the STZ-induced islets destruction and restored the number of islet cells that secreted insulin to the level of the control. The contents of total polyphenol and total flavonoids in 1g dry mass of DML extracts(DLW, DML leaves hot Water extracts; DLE, DML leaves ethanol extracts; DSW, DML stems hot Water extracts; DSE, DML stems ethanol extracts) were DLW (19080.51㎍), DLE (12561.03㎍), DSW (12207.18㎍), DSE (10266.66㎍) of gallic acid equivalents and DLW (1018.90㎍), DLE (803.79㎍), DSW (228.83㎍), DSE (220.68㎍) of quercetin equivalents, respectively. In addition, the antioxidant and DPPH radical scavenging activity of DML extracts IC50 were DLE (243.33㎍/㎖), DLW (212.70㎍/㎖), DSW (308.30㎍/㎖), DSE (317.07㎍/㎖). These results imply the intake of DML hot Water extracts could contribute to attenuate clinical symptoms of diabetes mellitus and improves β-cell proliferation and prevents the death of β-cells in STZ-induced diabetic rats.