Provided is a novel agent for promoting osteogenesis and/or inhibiting bone resorption, which: can be directly taken from daily meals by mouth for long periods without any trouble in taste; directly impart a promoting effect on osteogenesis and an inhibiting effect on bone resorption to the bone; and can be expected to have therapeutic effects for preventing or ameliorating/treating various bone diseases. The above agent includes, as an active ingredient, any one or more of .beta..sub.2-microglobulin, histone, complement component 3, monocyte chemotactic protein 1, lysozyme, ribonuclease, prothrombin, cytochrome P-450, plasminogen, transferrin, thrombin, plasmin, complement component 4, and .beta. defensin, and enzymatic digestion products thereof. Those substances have a remarkable inhibiting effect on bone resorption by osteoclasts and/or a promoting effect on osteogenesis via promotion of the proliferation and differentiation of osteoblasts.