The present invention addresses the problem of providing a therapeutic agent for abdominal aortic aneurysms, with which pharmacotherapy is possible.The present invention provides a therapeutic agent for an aortic aneurysm comprising, as an active component, (−;)-6-[3-[3-cyclopropyl-3-[(1R,2R)-2-hydroxycyclohexyl]ureido]propoxy]-2(1H)-quinolinone or a salt thereof, or a solvate of these.