Medicament being useful as a fibrosis inhibitor for organs or tissues, which comprises a compound of the formula (I): wherein Ring Z is optionally substituted pyrrole ring, etc.; W2 is —CO—, —SO2—, optionally substituted C1-C4 alkylene, etc.; Ar2 is optionally substituted aryl, etc.; W1 and Ar1 mean the following (1) and (2): (1) W1 is optionally substituted C1-C4 alkylene, etc.; Ar1 is optionally substituted bicyclic heteroaryl having 1 to 4 nitrogen atoms as ring-forming atoms: (2) W1 is optionally substituted C2-C5 alkylene, optionally substituted C2-C5 alkenylene, etc.; and Ar1 is aryl or monocyclic heteroaryl, which is substituted by carboxyl, alkoxycarbonyl, etc. at the ortho- or meta-position thereof with respect to the binding position of W1, or a pharmaceutically acceptable salt thereof.