This invention provides the synthesis of nanogel-apatite nanofine particles, which are a composite of nanogel and apatite fine particles, and its use. Based on finding about hydrophobilized polysaccharide nanogel, novel various organic-inorganic hybrid nanofine particles (nanogel-apatite nanofine particles) with regulated nanostructures could be synthesized from relatively monodisperse calcium phosphate nanofine particles by alternate addition of calcium ions and phosphoric acid ions or a novel method (a pH-gradient method) utilizing CO2 gas, using nanogel and its composite as a template.