Since the resistance factors for the effect of vitamin D increases by aging, ingestion of various nutrition factors, such as calcium, and vitamin D is important for prevention and medical treatment of osteoporosis. 1 alpha 25-dihydroxyvitamin D(3) known as active form of vitamin D can stimulate calcium absorption from intestine and also it is used for the medical treatment of osteoporosis. The vitamin D action for the regulation of bone and mineral metabolism changes with the sufficiency states or the amounts of ingestion of vitamin D. Therefore, the action as a medicine is not simple. This article reviews the effect and its optimum ingestion amount of activated vitamin D in osteoporosis medical treatment.