Highly surfaced and porous hydroxyapatite body was artificially formed on the surface of a shell through a reaction with phosphatic solutions. As a result of qualitative observation, hydroxyapatite seemed to be crystallized by solution-precipitation process accelerated by the nucleation surface of a shell. The process of formation of hydroxyapatite layer was as follows. 1. Dense nucleation and growth on the surface of solid phase 2. Formation of microporous layer by contact and entanglement between crystallines 3. diffusion of solution through the porous layer and thickness growth of layer towards inside.