Bone is a dynamic tissue that is regulated by the balance between bone-resorbing osteoclasts and bone-forming osteoblasts. Curcumin isolated from Kang-hwang (Turmeric) is widely used as a foodstuff, cosmetic, and medicine. However, the effect of curcumin isolated from Kang-hwang in osteoclast differentiation remains unknown. In this study, we sought to examine the role of curcumin in osteoclast differentiation. Here we show that curcumin greatly inhibited RANKL-mediated osteoclast differentiation in osteoclast precursors without cytotoxicity. RANKL induced the phosphorylation of p38 and JNK mitogen-activated protein kinase (MAPK) and mediated $I-{kappa}B$ degradation in bone marrow macrophages (BMMs). However, RANKL-mediated p38 MAPK phosphorylation was inhibited by the addition of curcumin. Curcumin inhibited the mRNA expression of TRAP, c-Fos, and NFATc1 in BMMs treated with RANKL. Furthermore, the protein expression of c-Fos and NFATc1 induced by RANKL was suppressed by curcumin treatment. Taken together, our results suggest that curcumin may have a potential therapeutic role in bone-related diseases such as osteoporosis by inhibiting osteoclast differentiation.