A film-forming method includes: a) discharging a liquid including a film material on an object so as to form a liquid film made of the liquid; b) irradiating the liquid film with light and thus detecting light from the liquid film so as to measure distribution of an optical constant, which is related to a film thickness of a thin film, with respect to the liquid film; and c) drying the liquid film on the object so as to form the thin film by converting the distribution of the optical constant into distribution of a temperature of the liquid film based on converting information that relates the optical constant of the liquid film to the temperature of the liquid film and thus forming the distribution of the temperature on the liquid film.