An $alpha$-glucosidase inhibitor, CK-4416, was identified from the culture broth of Streptomyces sp. CK-4416. CK-4416, which had some specificity against intestinal disaccharidases, especially sucrase and matlase activities, was purified by adsorption and cationic ion exchange chromatographies. The molecular formula was determined to be $C_{37}H_{63}NO_{30}$ (MW 1001.31) by FAB-MS and NMR analyses. In vitro studies found CK-4416 to show a potent inhibitory activity against sucrase and maltase, but it had low inhibition against $alpha$-amylase.