The present invention relates to uses of Macrolactin A produced by Bacillus polyfermenticus KJS-2 (KCCM 10769P), which is a new bacillus strain, as an antibiotic. Macrolactin A of the present invention, which is produced by Bacillus polyfermenticus KJS-2, shows a broad spectrum of antibiotic activity against a variety of microorganisms and fungi, and is proved to be very efficient for the inhibition of particularly vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus Aureus (MRSA) that are multidrug-resistant bacteria. The antibiotic Macrolactin A produced by Bacillus polyfermenticus KJS-2, can be used as an excellent antibiotic against vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus Aureus (MRSA), and thus the present invention is a very useful invention for medical industry.