Provided is an excellent prophylactic or therapeutic agent for an inflammatorydisease. Specifically disclosed is a prophylactic or therapeutic agent foran inflammatory disease, which comprises a thymidine phosphorylase inhibitoras an active ingredient (when the thymidine phosphorylase inhibitor is 5-chloro-6-(2-iminopyrrolidin-1-yl)methyl-2,4(1H,3H)-pyrimidinedione or a salt thereof, inflammatory bowel disease is excluded fromthe category of the inflammatory disease).