Disclosed is an esophageal stent placed in a stenosed part of the esophagus having a flexible tube to prevent the reverse flow of gastric contents from the stomach is coupled to the lower end of the esophageal stent. The flexible tube has an inside membrane and an outside membrane adhered to each other, thus having a twofold structure with at least one core longitudinally placed between the adhered inside and outside membranes while the core extends from the upper end toward the lower end of the flexible tube. Thus, the flexible tube is prevented from being inverted, and prevents the reverse flow of the gastric contents, and maximizes the operational reliability of the esophageal stent. The flexible tube does not cause a patient pain or discomfort due to frictional contact of the tube with the inner surface of the stomach when the tube moves in the stomach.