PROBLEM TO BE SOLVED: To provide a novel antibacterial activity promoter promoting antibacterial activity of an antibacterial agent, and an anti-infective agent containing the antibacterial activity promoter.SOLUTION: The antibacterial activity promoter promoting antibacterial activity of an antibacterial agent, consists of apolipoprotein A-I, apolipoprotein A-II, or phosphatidylethanolamine, or pharmaceutically acceptable salts thereof and an anti-infective agent contains the above antibacterial activity promoter and an antibacterial agent in which antibacterial activity is promoted by the antibacterial activity promoter.