A 2-iminopyrrolidine derivative represented by the formula: ##STR00001## {wherein ring B represents a benzene ring, pyridine ring, etc.; R.sup.101 R.sup.103 represent hydrogen, halogen, C.sub.1-6 alkyl, etc.; R.sup.5 represents hydrogen, C.sub.1-6 alkyl, C.sub.1-6 alkoxy-C.sub.1-6 alkyl, etc.; R.sup.6 represents hydrogen, C.sub.1-6 alkyl, C.sub.1-6 alkyloxycarbonyl, etc.; Y.sup.1 represents a single bond, --CH.sub.2--, etc.; Y.sup.2 represents a single bond, --CO--, etc.; and Ar represents hydrogen, a group represented by the formula: ##STR00002## [wherein R.sup.10--R.sup.14 represent hydrogen, C.sub.1-6 alkyl, hydroxyl, C.sub.1-6 alkoxy, etc.; and R.sup.11 and R.sup.12 or R.sup.12 and R.sup.13 may bond together to form a 5- to 8-membered heterocyclic ring], etc.}, or a salt thereof.