the present invention provides an extract obtained by extracting a plant belonging to the genus epimedium sp . with a mixed solvent of water and a water - miscible organic solvent or with water , defatting the obtained aqueous extract and collecting a high - molecular compounds - containing fraction from the defatted aqueous extract , a process for preparation of this extract , an antibacterial agent comprising this extract as an effective component and an antibacterial therapy by using this extract .