To find novel natural materials presenting therapeutic activities against diabetes and obesity, we screened various herb extracts using a chip screening allowing the determination of PTP1B inhibitory effects of the tested compounds using insulin receptor (IR) as the substrate. Cudrania tricuspidata leaves (CTe) had a strong inhibitory effect on PTP1B activity and substantially inhibited fat accumulation in 3T3-L1 cells. This evidence concerns the gene PTPN1 and diabetes mellitus.