Abstract: A 1,2,4-oxadiazole derivative is represented by the following general formula (I): ##STR1## wherein R.sup.1 represents a lower alkyl or cycloalkyl group, a lower alkyl group substituted with a halogen atom, a lower alkylamino group or a phenyl group; R.sup.2 represents a hydrogen atom, a lower dialkylamino group, a cyclic alkylamino group, a cyclic amino group having an oxygen or nitrogen atom in the ring, a phenyl group which may be substituted with a halogen atom, a pyridyl group, an imidazolyl group, an alkylimidazolyl group, a benzimidazolyl group or a 2-oxopyrrolidinyl group; and n is 1, 2 or 3. The derivative has excellent monoamine oxidase-inhibitory activity and is effective as a medicine for treating Parkinson's disease.