Mugwort has been known as a traditional substitutive foodstuff and as showing a physiologically beneficial function to a human being. Therefore, effect of mugwort extract in terms of mutagenicity and desmutagenicity was investigated to berify its function. Ethanol extract from mugwort did not exhibit any mutagenicity. On the contrary, inhibitory effects of the ethanol extract were observed on mutagenicity induced by aflatoxin $B_{1}(AFB_1)$, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole(Trp-P-1), 3-amino-1-methyl-5H-pyrido[4,3-b]indole(Trp-P-2) and 2-nitroflourene(2NF) using Salmonella typhimurium reversion assay. On direct-acting mutagen(2NF, 3${mu}$g/plate), ethanol extract showed a slight inhibitory effect of 19.7~22.9%, however on indirect-acting mutagen such as AFB1(2${mu}$g/plate), Trp-P-1(1${mu}$g/plate) and Trp-P-2(1${mu}$g/plate), we observed higher inhibitory effect of 47.9~61.2%, 64.1~70.7%, 67.4~78.7%, respectively. Step-wise fractionation of the ethanol extract was done by using hexane, chloroform, ethyl acetate and water to obtain effective fraction. Among them, hexane, chloroform, and ethyl acetate fractions showed high inhibition of 63.0~80.0%, 77.5~82.1%, and 68.5~83.1%, respectively on the mutagenicity of $AFB_1$ in Sal. typhimurium TA98. Consequently, these results indicated that mugwort extract contains some compound(s) which may show desmutagenicity.