A thiazole derivative which is excellent in an active oxygen inhibitory effect, represented by general formula (I), wherein R¹ represents phenyl which may be substituted by 1 to 3 lower alkoxy groups, and R² represents an optionally substituted pyridylcarbonyl group, a 5- to 15-membered mono-, di- or tricyclic heterocyclic group bearing 1 to 3 nitrogen, oxygen or sulfur atoms, or a substituted phenyl group.