Alumina glazed with a bioactive glass reacted in Simulated Body Fluids(SBF) to investigate the behavior of hydroxyapatite formation on the glass coat layer. Various crystalline phases were found depending on the firing temperatures when the bioactive glass coat was heat-treated. The glass coat was crystallized into ${eta}$-wollastonite and apatite when fired at 1100$^{circ}C$, and ${alpha}$-wollastonite and apatite when fired at 1200$^{circ}C$. Those samples reacted in SBF, and it is observed that hydroxyapatite developed on the surface of the crystallized glaze. Its formation was much easier in the sample with ${alpha}$-wollastonite than with ${eta}$-wollastonite. This is because that the ${alpha}$-wollastonite dissolves more easily than ${eta}$-wollastonite does in SBF.