Osteoporosis is a metabolic bone disease associated with an imbalance of bone remodeling. Osteoporosis is characterized by decreased bone mass and increased bone fractures. In this study, we investigated the effects of horse bone extracts (HBEs) in vivo. Horse bone was extracted with 80% alcohol (HBE-A) at $100^{circ}C$ or water (HBE-W) at $120^{circ}C$. Animal model of postmenopausal osteoporosis was used, in which osteoporosis was induced by ovariectomy of female S.D. rats (female rats were divided into 5 groups), and HBEs were administered to ovariectomized rats every day for 8 weeks. After 8 weeks, the rats were sacrificed and the following osteoporotic factors were measured: body weight, bone mineral density (BMD), uterine/body weight ratio, serum estradiol (E2), and serum alkaline phosphatase (ALP). The results showed that the administration of HBE-W decreased the changes of body weight in ovariectomized rats. HBE-W increased the uterine/body weight ratio and BMD. In addition, HBEs decreased the ALP. Therefore, HBEs may be used for the prevention or treatment of bone disease.