The calcium-phosphate type hydroxyapatite is in the form of spherulites having a mean particle diameter of 0.5 to 50 um and preferably 1 to 10 mu m. The spherulites are aggregates mainly of acicular crystallites belonging to a series of hexagonal systems and having unit lattice constants of 9.58 +/- 0.08 ANGSTROM (0.958+/-0.008 nm) for the a axis and 7.00 +/- 0.05 ANGSTROM (0.700+/-0.005 nm) for the c axis. The spherulitic hydroxyapatite is produced by granulating a calcium-phosphate type hydroxyapatite in the form of a gel and then firing the granular apatite at 400 to 700 DEG C, preferably at 500 to 600 DEG C and desirably in the presence of oxygen or air. |