An antibacterial agent comprising a compound represented by the following general formula (I), which can exhibit potent antibacterial activity against bacteria that have acquired resistance to quinolones (in the formula, R1 and R4 represents hydrogen atom, hydroxyl group, or a lower alkoxy group R2 and R3 represents hydrogen atom or hydroxyl group W represents hydrogen atom, a lower cyclic alkyl group, or a lower alkoxy group R1′ and R5′ represents hydrogen atom R2′ and R3′ represents hydrogen atom, hydroxyl group, or a lower alkoxy group and R4′ represents hydrogen atom or hydroxyl group).
