The present invention relates to a screening method for a compound and includes a step of detecting binding between a vitamin D receptor and CDP. A novel method enabling screening in vitro of a compound having strong bone forming action and low side effects, a compound participating in osteoblast differentiation and selected by the method of screening, a therapeutic agent containing the compound for diseases intervening in the increase in vitamin D-mediated transcriptional activity by a complex of a vitamin D receptor and CDP, and a kit for performing the screening method are provided.