A hematopoietic tissue, bone marrow, is located inside the bone. The functional interaction between skeletal and hematopoietic systems has been revealed recently. The roles of osteoblasts as a component of hematopoietic microenvironment have been intensively studied, which is now an important research field. On the other hand, the functions of hematopoietic cells as regulators of osteoblasts have also been elucidated gradually. This review describes how innate immune cells such as macrophages and neutrophils take part in bone metabolism.