A coating technology was developed to form hydroxyapatite (HAp) films on polylactic acid (PLA) plates by aerosol beam irradiation. The aerosol beam was composed of HAp particles of submicron size and helium gas. HAp films were produced at incidence angles of 0, 10, 20, and 30°, but the HAp films did not have good adhesion to the PLA plate when incidence angles were 0, 10, and 20°. To increase the adhesion strength between the HAp film and the PLA plate, the HAp film produced on the plate with an incidence angle of 30° was heated in an electric furnace. In vitro assessments using simulated body fluid (SBF) were performed to investigate the bioactivity of the HAp-coated PLA plate. The heat-treated HAp film did not peel off from the plate throughout the SBF test. The surface morphology and the crystallinity of the film produced in the SBF suggest that the HAp-coated PLA plate is bioactive.