PROBLEM TO BE SOLVED: To provide an antibacterial agent exhibiting strong antibacterial activity against a bacterium resistant to quinolones.SOLUTION: An antibacterial agent comprises a flavone compound represented by the general formula (I) (where, R, RRand Rrepresent a hydrogen atom, a hydroxy group or a lower alkoxy group； R, Rand Rrepresent a hydrogen atom or a hydroxy group； Rrepresents a hydrogen atom, a lower cyclic alkyl group or a lower alkoxy group； and R' and R' represent a hydrogen atom) as an active ingredient. An antibacterial agent, where the compound is combined with a quinolone, prevents appearance of a resistant bacterium.【課題】キノロン類に耐性化した細菌に対して強い抗菌力を発揮できる抗菌剤の提供。【解決手段】一般式（Ｉ）で表されるフラボン化合物を有効成分として含む抗菌剤（Ｒ１、Ｒ４Ｒ２’及びＲ３は水素原子、水酸基、又は低級アルコキシ基を示し；Ｒ２、Ｒ３及びＲ４’は水素原子又は水酸基を示し；Ｒ５は水素原子、低級環状アルキル基、又は低級アルコキシ基を示し；Ｒ１’及びＲ５’は水素原子を示す）。更に、該化合物とキノロン類を組み合わせて、耐性菌の出現を阻止する抗菌剤。【選択図】なし
