A method for treating a microorganism or inflammation caused by the microorganism includes administering or applying a composition comprising an antimicrobial peptide with the amino acid sequence of SEQ ID NO: 1 to a subject in need thereof. Because the antimicrobial peptide with the amino acid sequence of SEQ ID NO: 1 exhibits an excellent antimicrobial activity against Gram-negative bacteria and Gram-positive bacteria and also low cytotoxicity for human erythrocytes, it can be advantageously used for various applications.