In order to develop a antimicrobial agent, dried Sophora flavescens Ait. was extracted with several solvents, and then antimicrobial activity was investigated.The minimal inhibitory concentration (MIC) of the extracted substance against microorganisms were also examinedAntimicrobial activity of the initial methanol extract from the sample was the strongest compared to those of other solvent extracts such as H2O, n-hexane, chloroform, Et acetate and methanol.The methanol extract had strong growth inhibition activity against gram-pos. bacteria (MIC, 25-50 μg/mL) such as B. subtilis and S. aureus.Among gram-pos. bacteria tested, B. subtilis was the most susceptible to the extracted substance.The antimicrobial activity of the methanol extract from the sample had strong growth inhibition activity against gram-neg. bacteria such as P. aeruginosa (MIC, 25 μg/mL).