A therapeutic drugs for bone diseases containing as the active ingredient staniocalcin 1 which is found to have an effect of increasing bone mass. This drug for bone diseases is effective for bone diseases accompanied by anomalous osteogenesis or reduction in bone mass, such as osteoporosis, traumatic bone injuries, osteomalacia, rheumatic bone diseases, cancer-associated bone diseases, bone diseases associated with phosphorus metabolic error or calcium metabolic error, rachitis and arthrosis deformans.