Abstract: To produce a high quality thin film by effectively removing the particles from the emitted substance and the oxygen retained under a high vacuum during the production of the thin film by laser ablation, there is provided a process for producing a thin film on a substrate by laser ablation in a vacuum chamber in which a laser beam is irradiated to a target to cause emission of a substance from the target and allowing the emitted substance to deposit on the substrate to grow a thin film on the substrate by laser ablation, the process including irradiating an ion beam to at least one of the substrate and a plume of the emitted substance formed between the substrate and the target.