To provide an excellent agent for prevention or treatment of an inflammatory disease. The agent for prevention or treatment of an inflammatory disease contains a thymidine phosphorylase inhibitor as an active ingredient, wherein when the thymidine phosphorylase inhibitor is 5-chloro-6-(2-iminopyrrolidin-1-yl)methyl-2,4(1H,3H)-pyrimidinedione or a salt thereof, the inflammatory disease is an inflammatory disease other than inflammatory bowel disease.