PURPOSE: To provide a new benzothiazepine derivative useful as an anti-ulcer agent or stomachic agent having a protease-inhibiting action and a mucosa- protecting action as action mechanisms and its physiologically acceptable salt.

CONSTITUTION: A benzothiazepine derivative of formula I (R1 is H, alkyl, phenyl, substituted benzene, carboxyalkyl including carboxymethyl, hydroxyalkyl including hydroxymethyl; R2 is H, halogen, alkyl, phenyl, substituted benzene, hydroxyalkyl) and its physiologically acceptable salt, e.g. 5-carboxymethyl-2- phenyl-1,5-benzothiazepine-4-one of formula 4. The compound of formula 3 or 4 among the compound of formula I can be synthesized by a known method using a compound of formula 2 as a starting raw material. The compound has a remarkable anti-ulcer action and a slight stomachic action in which the removal of attacking factors due to its protease-inhibiting action and the reinforcement of protecting factors due to its mucosa-protecting action act as action mechanisms. The compound can be used for the symptomatic treating or preventing therapy of digestive organ ulcers.