A FGF-2-apatite composite layer was formed on hydroxyapatite (HAP) ceramics using supersaturated calcium phosphate solutions containing various amounts of potassium chloride. The optimum conditions for the formation of the composite layer were determined by using cytochrome C (cyt C), one of the dummy proteins of FGF-2, and an immersion solution with a Ca/P molar ratio of 0.19 and a potassium chloride concentration of 8 mM. The amounts of cyt C and FGF-2 immobilized in the composite layer were 1.28±0.30 and 3.18±0.01 µg cm-2, respectively. The release of FGF-2 from the composite layer continued for at least 3 days. It was considered that the release period of FGF-2 could be extended to day 10 because the release of cyt C continued for at least 10 days. When the composite layer is formed on commercial bone substitutes, it is expected that the promotive effect on bone formation around the bone substitutes will continue for at least 10 days.