To provide a film formation method capable of forming an organic compound layer with a high purity and a high density.

A film forming method for depositing an organic compound over a substrate provided in a film formation chamber, wherein degree of vacuum in the film formation chamber is kept higher than 510-3 Torr, and after formation of a film by depositing an organic compound material over the substrate from a deposition source provided opposite to the substrate, the substrate is carried out in a treatment chamber different from the chamber for the film formation without being exposed to the atmospheric air, and degree of vacuum in the film formation chamber is kept higher than 510-3 Torr, and also, the substrate is heated to decrease a gas in the film.