In this study, cytotoxicity of cadmium on NIH 3T fibroblasts was utilized in order to discover antitoxic compound in methanol extract of Sophora fIavascens Ait. There were treatment groups; control (medium only), $MTT_{50}$ group and five experimental groups. MTT {3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H- tetrazoliumbromide} assay was performed to evaluate the cytotoxicity of cell organelles and $IC_{50}$ was also measured. Accordingly we have examined the detoxification effects of methanol extract of S. flavescens Ait. and leachianone A (LA) on cadmium-treated NIH 3T3 fibroblasts ($IC_{50}=;12.5{mu}M$) to observe morphological changes by the light microscopy. Both S. flavescens Ait. methanol extract and LA showed inhibitory effects on cadmium-induced cytotoxicity. Furthermore, LA showed dose-dependency in detoxication. From these results, it is conceivable to suggest that LA from S. flavescens Ait. methanol extract is a potential antitoxic agent.