Sopungsungi-won has been used as a traditional medicine for diabetes and it has been proved to be a potential remedy for type 2 diabetes mellitus. We previously reported that water extract of Sopungsungi-won exhibits anti-diabetic effects both in vivo and in vitro experiments. In the present study, we have chosen to examined anti-apoptotic effect of Rheum undulatum, which is the main component of Sopungsungi-won, on pancreatic β-cells, HIT-T15, against hydrogen peroxide (H2O2). oxidative stress. To investigate the anti-apoptotic effect of Rheum undulatum water extract (RUWE) against H2O2-induced apoptosis in pancreatic β-cell line of hamster, HIT-T15, MTT assay, DAPI staining, TUNEL assay, RT-PCR and caspase-3 enzyme assay were performed. The morphological analysis demonstrated that cells treated with H2O2 exhibited classical apoptotic features, while such changes was reduced in cells pre-treated with RUWE. In addition, RUWE pre-treated cells prior to H2O2 treatment induced increase of levels of bcl-2 expression and decrease of caspase-3 enzyme activity compared to cells treated with H2O2 only. These results provide the possibility of usage of RU in patients with progressively deteriorated diabetes.