Provided is a novel bacteriophage FCJ20 (KCCM11362P). In addition, the present invention relates to an antibacterial composition including the bacteriophage FCJ20 (KCCM11362P) as an active ingredient. Further, the present invention is a method of preventing and/or treating infectious diseases by enterotoxigenic Escherichia coli in animals except for humans using the bacteriophage FCJ20 (KCCM11362P) or the antibacterial composition containing the bacteriophage FCJ20 (KCCM11362P) as an active ingredient.