Six prenylated xanthones, cudraxanthone B (1), isocudraxanthone K (2), cudraxanthone H (3), cudratricusxanthone A (4), cudraxanthone L (5) and macluraxanthone B (6), have been isolated from the MeOH extract of Cudrania tricuspidata root barks. The evaluation for antibacterial effect of compounds 1-6 against the pathogenic microorganisms concerning with public health or zoonosis was conducted. Of these, compound 4 showed significant antibacterial effect in disk diffusion method.