Provided are: a composition for inhibiting the renin-angiotensin system; a use of said composition as a substance for inhibiting the renin-angiotensin system; and a method for inhibiting the renin-angiotensin system. It has been discovered that a specific cyclic dipeptide or a salt thereof exhibits renin-angiotensin-system inhibiting action. The present invention provides a novel and effective means for contributing to inhibiting blood pressure elevation.