[PROBLEMS] To provide a compound which can be used as a medicinal agent, particularly a therapeutic agent for irritable bowel syndrome (IBS). [MEANS FOR SOLVING PROBLEMS] It is found that a tetrahydroisoquinolin-1-one derivative having an amide group at position-4 or a pharmaceutically acceptable salt thereof has an excellent antagonistic activity on a bombesin-2 (BB2) receptor. It is also found that the tetrahydroisoquinolin-1-one derivative is highly effective on stool abnormality. Therefore, the tetrahydroisoquinolin-1-one derivative is useful as a therapeutic agent for a disease associated with a BB2 receptor, particularly IBS.
