Methanol extract (MeOH), n-hexane (Hx), chloroform ($CHCl_3$), ethyl acetate (EA), butanol (BuOH) and aqueous ($H_2O$) fractions of Eucommiae Cortex including geniposidic acid (GA), geniposide (GP) and aucubin (AU) were tested for their therapeutic efficacy on osteoporosis. The contents of GA, GP and AU in the cortex and leaf of Eucommia ulmoides Oliver were quantified by HPLC. The effect of Eucommiae Cortex on the induction of growth hormone (GH) release was studied by using rat pituitary cells. The proliferation of osteoblast-like cells increased by herbal extracts was assayed using a tetrazolium (MTT), alkaline phosphatase (ALP) activity, and [$^3H$]-proline incorporation assays. The inhibition of osteoclast was studied by using the coculture of mouse bone marrow cells and ST-2 cells. As a result, the GA, GP and AU were present in the cortex more than in the leaf of E. ulmoides Oliver. The MeOH (1mg/mL), Hx, $CHCl_3$ and EA fractions (each 20 $mu$ g/mL) had potent induction of GH release. The $CHCl_3$ exhibited the potent proliferation of osteoblasts. The AU, GP and GA were increased proliferation of osteoblasts. In addition, GA ($IC_{50}: 4.43{ imes}10^{-7}$M), AU and GP were significantly inhibited proliferation of osteoclast. In summary, it is thought that the components in a part of the fractions of Eucommiae Cortex participate in each step of mechanism for activating osteoblast to facilitate osteogenesis, and suppress osteoclast activity to inhibit osteolysis.