Wnt ligands activate β-catenin-dependent canonical and -independent non-canonical signaling pathways. Recent studies established importance of Wnt/β-catenin signaling in bone accrual. Antibodies against the Wnt inhibitor sclerostin and those against the Wnt inhibitor Dickkopf-1 have been shown to be effective for increasing bone mass. In addition to their effects on bone formation, roles of Wnt signals in bone resorption are gradually clarified. In this review, we would like to introduce recent advances in roles of Wnt signals in osteoclast formation and functions and regulation of sclerostin expression by osteoclasts.