Artificially synthesized antimicrobial peptide that does not occur naturally is provided by the present invention. The antimicrobial peptide includes one unit, two units or more units of amino acid sequence composed of the following 8 amino acid residues: (R or Q)-(L or F or I)--I--K-(L or F or I or V)-L-Y-Q; and/or, modified sequence composed of said sequence with partial modification.