Hydroxyapatite powders were prepared by oyster shells and phosphoric acid. They were heat treated at the $1300^{circ}C$ for 2 hrs. Only hydroxyapatite phases were observed by the XRD analysis. XRF confirmed that the prepared hydroxyapatite composed with 63.2wt% CaO and 35.7wt% $P_2$$O_{5}$ . In the ICP test, small amount of heavy metals were detected as low as 0.009 ppm Ti and 0.002 ppm Ba. The test of bone density was done in human body during three months. As the periods of medication progressed, the bone density was increased.