PROBLEM TO BE SOLVED: To provide a thin film forming apparatus for forming a thin film containing calcium and phosphorus on a hard tissue such as enamel without invading a living body, by which the hard tissue such as enamel can be regenerated in a noninvasive manner through ionization and recalcification of calcium and phosphorus contained in the thin film by saliva or the like.SOLUTION: The thin film forming apparatus 1 includes: a laser irradiation part 11 emitting laser L a target 12 formed of a biocompatible ceramic and a target holding part 13 for holding the laser irradiation part 11 and the target 12 so that the target is located on the laser irradiation line and atoms, molecules, clusters, and droplets P scattered from the target by the irradiation with laser, are deposited on the hard tissue (tooth substance T).
