Hydroxyapatite (HAp) films were formed on a titanium substrate in aqueous solutions by the thermal substrate method controlling the substrate temperature and a cathodic electrolysis method supplying hydroxide ions. A local increase in temperature on substrate and the supply of calcium, phosphate, and hydroxide ions near the substrate accelerate the HAp film formation on the substrate in aqueous solutions at ambient temperature and pressure. The HAp can be directly coated only on the substrate quickly by heating the substrate in an aqueous solution. In the cathodic process, reduction of hydrogen peroxide forms hydroxide ions, which results in the formation of a flat, plate-like HAp film.