The antimicrobial activity of mugwort(artemisia asiatica Nakai) was investigated. The methanol extract or dried mugwort was fractionated to hexane, chloroform, ethylacetate, butanol, and aqueous fractions. The hexane fraction among these fractions showed the hifhest inhibitory effect on the growth of microorganisms such as Bacillus subtilis, Escherichia coli, Staphylococcus aureus and Lactobacillus plantarum. Bacillus subtilis, Escherchia coli, and Staphylococcus aureus were completely inhibited at a concentration of 250, 500 , and 750$mu extrm{g}$/ml respectively. The hexane fraction was further fractionated into 16 subfractions by silica gel column and thin layer chromatography(TLC). The subfraction No. 8, 9, and 10 on TLC exhibited high antimicrnial activity. At 3rd fractionation, subfraction No. 2 inhibited the growth of microorganisms at 500$mu extrm{g}$/ml. Heptadecane, dodecamethyi cyclohexasiloxane, (E,E)-2,4-decadienal, dodecamethul pentasiloxane, coumarin, 5,6,6,6a-tetrahydro-4,4,7a-trimethyl-2(4H)-benzofuranone, neophytadiene, tridecanoic acid, methyl ester, 2-methyl-4,5-nonadiene, (Z,Z)-9-12-octadecadienoyl chloride, and bis(2-ethylhexyl) were identified from this antimicrobial fraction by GC-MS.