[Problem] The problems to be solved by the invention is to provide antibacterial agents originated from natural products that are safe for regular use with potent antibacterial activity, and antibacterial compositions containing said antibacterial agents. [Solution] Antibacterial agents containing Eysenhardtia adenostylis extract or isoflavan compounds. Also, antibacterial agents containing Eysenhardtia adenostylis extract or isoflavan compounds as active ingredients. Said antibacterial agents can be applied to products such as cosmetics, including quasi-drugs, pharmaceuticals and foods. Further, antibacterial compositions containing said antibacterial agents, Eysenhardtia adenostylis extract or isoflavan compounds, and said compositions include cosmetics, including quasi-drugs, pharmaceuticals and foods.