Provided is a composition that, even when used in a very small amount, has the effect of improving bone density and promoting bone growth, and has few side effects, and also provided are a pharmaceutical preparation for promoting bone growth, functional food product, and health food product containing the composition as an active ingredient. The composition can be obtained from any plant part selected from the group consisting of the bud, leaf, bark or wood of a plant belonging to the family Magnoliaceae. The composition comprises at least one selected from the group consisting of fargesin and physiologically acceptable salts, hydrates, and glycosides thereof. The pharmaceutical preparation, functional food product, and health food product comprising this composition as an active ingredient sufficiently improve bone density and promote bone growth, even when used in small amounts, and therefore realize preventive and/or therapeutic effects against bone disease etc. such as osteoporosis.
