Objectives: This study was conducted to evaluate the inhibitory effect of Melia Fructus extract on osteoclast differentiation. Methods: MTT-assay was performed to estimate cytotoxicity of Melia Fructus extract in BMMs stimulated with M-CSF. TRAP staining, TRAP activity and Real-time PCR were performed to know the inhibitory effect on osteoclast differentiation. Actin ring formation were analysed to observe the effect of Melia Fructus extract. Results: Melia Fructus extract decreased the number of TRAP positive cells and the expression of NFATc1 gene, c-Fos gene, TRAP and OSCAR in BMMs stimulated with RANKL. Melia Fructus extract has no cytotoxicity at the concentration used in this study. Melia Fructus extract restrained the formation of actin ring. Melia Fructus inhibited NF-${kappa}B$ activity by inducing degradation of p-$IkB{alpha}$. Conclusions: Melia Fructus has the inhibitory effect of osteocalst differentiation and bone resorption. Further studies are needed to treat osteoporosis by herbal medicine containing Melia Fructus.