To provide a drug having excellent antibacterial activity against Gram-positive bacteria and Gram-negative bacteria and also being excellent in terms of safety.A compound represented by the following formula (I) or a salt thereof: wherein R represents hydrogen atom m represents an integer of 1 or 2 n represents an integer of 0 or 1 Ar1 represents a bicyclic heterocyclic group represented by the following formula: [Formula 2] wherein: Aa represents nitrogen Ab and Ac represent CH R1 represents a methoxy group, a difluoromethoxy group, a halogen atom, or a cyano group R2 represents a hydrogen atom or a halogen atom Ar2 represents a bicyclic heterocyclic group represented by the following formula:提供對革蘭氏陽性菌及革蘭氏陰性菌具有絕佳抗菌活性且具絕佳安全性的藥物。一種由下列式(1)代表的化合物或其鹽類:其中,R代表氫原子;m代表整數1或2;n代表整數0或1;Ar1代表由下式所代表的雙環雜環基:其中:Aa代表氮;Ab及Ac代表CH;R1代表甲氧基、二氟甲氧基、鹵素原子、或氰基;R2代表氫原子或鹵素原子;Ar2代表由下列分子式所代表的雙環雜環基:
