A thickness adjustment device for thin-film coating is revealed. The thickness adjustment device for thin-film coating includes a coating device, a support set, and a thickness adjustment unit. The coating device consists of a work piece conveyor that delivers a work piece, and a material supply unit that carries a coating material onto a surface of the work piece to form a film. The support set is connected to the coating device while the thickness adjustment unit is inserted through and mounted on the support set. The thickness adjustment unit includes a scrape part disposed correspondingly to the work piece and used for applying coating material to form the film. The thickness of the film is adjusted according to a controlling force or torque of the thickness adjustment unit that presses downward. Thus the film is coated on the work piece evenly and the film coating quality is increased.