Hydroxyapatite (HAp) has so high biocompatibility that it can be applied to fillings in orthopedic surgery and dental prosthodontics. Composites of HAp with active ingredients, e. g. protein or vitamin, are studied as scaffolds by many researchers. In general, microencapsulation is effective in keeping the composition constant during storage and making the handling in practical operation convenient. The interfacial reaction with using multiple emulsion is a typical method to prepare inorganic microspheres. We have found that HAp microspheres can be prepared by this method. The important factors are both the stability of the inner aqueous droplets and the diffusion of reactant species from the outer aqueous phase through the oil phase to the inner interface. The objectives of this study are to search for the optimum recipe to prepare stable emulsion and to know the relation between the preparation condition and the morphology of HAp produced. Thermodynamic calculation was used to understand the phase equilibrium. Dipotassium hydrogen phosphate aqueous solution was used as an inner aqueous phase, of which pH was controlled with potassium hydroxide. Benzene, cyclohexane, or toluene was used as an oil phase. Sorbitan monooleate or sorbitan monolaurate was used as a dispersion stabilizer for the inner aqueous droplets. These two solutions were mixed and stirred at 11000 rpm to prepare a w/o emulsion, of which stability was evaluated by measuring the change in the emulsion volume in a test tube. The w/o emulsion was poured into calcium nitrate solution, in which polyoxyethylene(20) sorbitan monolaurate has been dissolved as a dispersion stabilizer for the oil droplets, under stirring at 300 rpm to prepare a w/o/w emulsion. The final products were characterized with respect to the crystalline phase, yield, and morphology. The most stable w/o emulsion was obtained when cyclohexane dissolving sorbitan monooleate was adopted as the oil phase. Under this optimum condition, the agglomeration of the product was significantly decreased. TEM observation showed that each microsphere was composed of ribbon-like particles.