The present application relates to a novel bacteriophage having enterotoxigenic Escherichia coli-specific bactericidal effect and an antibacterial composition comprising same, the novel bacteriophage CJ_Eco_20-4 having enterotoxigenic Escherichia coli-specific bactericidal effect, and being superbly acid and heat resistant to allow wide use in antibiotics, feed and additives therefor, beverages and additives therefor, disinfectants, detergents, and the like to prevent or treat infectious diseases caused by enterotoxigenic Escherichia coli.