This study was conducted to search for the ${alpha}-glucosidase$ inhibitor from the natural products. In the previous study, the water extract of Gyrophora esculenta exhibited a potent inhibitory effect on ${alpha}-glucosidase$ activities. Then, by bioassay-guided fractionation followed by chromatographic separation of the water extract of Gyrophora esculenta, ${alpha}-glucosidase$ inhibitor was isolated as GE974. GE974 showed significant inhibitory activities on some kinds of ${alpha}-glucosidase$ in vitro. Its inhibitory mechanism seemed to be competitive for disaccharides. Also, it markedly inhibited ${alpha}-glucosidases$ of intestine separated from both nondiabetics and diabetics.