This invention provides a new film forming method in which, on the occasion that pressure is decreased by pressure decreasing means which was connected to a film forming chamber, and a film is formed by evaporating an organic compound material from a deposition source in the film forming chamber, minute amounts of gas (silane series gas) which comprises smaller particles than particles of the organic compound material, i.e., a material with a smaller atomic radius are flowed, and the material with a small atomic radius is made to be included in an organic compound film.