It is an object to provide a method for forming a thin film having a uniform thickness so as to follow asperities of a surface of a wafer to be processed and to provide a film-forming device used for the method. The film-forming device includes a treatment chamber for receiving a wafer and isolating the wafer from the air; a solvent-gas-supplying portion for supplying a solvent gas into the treatment chamber; a chuck for rotatably holding the wafer so that the downward-facing surface of the substrate is the surface on which a thin film is formed; a coating-solution-supplying portion for supplying a coating solution as a mist of charged particles toward the surface of the wafer; and a charging portion for charging the wafer with an electrical potential opposite to the charge of the particles.