The effects of MeOH extracts from 88 herbal medicines on monoamine oxidase (MAO) acitivity were investigated. MAO was purified from mouse brain and its activity was determined by fluorospectrophotometer using kynuramine as a substrate. The $K_m;and;V_{max}$ values (n=4) of MAO were $78.2{pm}4.0;{mu}M$ and $0.65{pm}0.05$ nmol/min/mg protein, respectively. Four MeOH extracts from Melilotus sauvelolens, Eupatorium lindleyanum Bupleurum longiradiatum and Sorbaria sirbiforia showed a strong inhibitory effect with less than $100{mu}g/ml$ in their $IC_{50}$ values on MAO activity. Six MeOH extracts including Agastache rugosa showed a mild inhibitory effect with 100~200${mu}$g/ml in their $IC_{50}$ values. Twenty-two MeOH extracts including Melandryum seoulense exhibited a week inhibition of MAO activity with 200~300${mu}$g/ml in their $IC_{50}$ values.