The effects of evodiamine on monoamine oxidase (MAO) activity were investigated. MAO was purified from mouse brain and the $K_m;and;V_{max}$ values of MAO were $78.5{pm}5.28{mu}M$ and $0.68{pm}0.07$ nmol/min/mg protein, respectively (n=4). Evodiamine at $30-120{mu}M$ showed an inhibitory effect on MAO activity using a substrate kynuramine with an $IC_{50}$ value of $104.2{mu}M$ (n=4). Evodiamine also exhibited a non-competitive inhibition on MAO. The $K_i$ value for evodiamine was $72.5{pm}10.8{mu}M$ (n=4). These results suggest that evodiamine partially contributes to the regulation of monoamine content.