Alkali earth hydroxyapatites (A-Hap: A = Ca, Sr, and Ba) containing Cu in the channel sites were synthesized by a Cu-loading and heat treatment method, and their thermal properties were investigated by thermogravimetry and high-temperature X-ray diffraction. Reversible incorporation/deposition of Cu in the channel sites of the apatites was observed. The behavior was accompanied with the oxidation/reduction of Cu at elevated temperatures in air.