To evaluate antimicrobial activity of Moutan cortex the compounds isolated from $CHCl_3$ and EtOAc fractions of Moutan cortex were subjected to eight pathogenic strains. Benzoic acid, witch was identified from the $CHCl_3$ fraction, had MICs with $625{sim}1,250;{mu}g/ml$ against all of the strains tested. Methyl gallate, p-hydroxy benzoic acid, gallic acid and $1,2,3,4,6-penta-O-gallyol-{eta}-D-glucose$, which were identified from the EtOAc fraction, showed the antimicrobial activity, and the methyl gallate had the widest antimicrobial activity with MICs of $625{sim}5,000;{mu}g/ml$ against all strains tested. p-Hydroxy benzoic acid showed MICs of $1,250{sim}2,500;{mu}g/ml$ against all of the strains tested except C.albicans. Gallic acid had the best antimicrobial activities with MICs against the Shigella dysenteriae and Streptococcus mutans-strains of 78.1 and $312.5;{mu}g/ml$, respectively, but not against the C. albicans. And $1,2,3,4,6-penta-O-gallyol-{eta}-D-glucose$ had the best antimicrobial activitie with MICs against the B. cereus, Staph. epidermidis and C. albicans strains of 39.1, 39.1 and $156.3;{mu}g/ml$, respectively, but not against the E. coli and Shig. Dysenteriae.