A re-forming process is carried out in which a material graphite film is heat-treated to not less than 2000° C. while the material graphite film is being pressured. Through the re-forming process, sag of a graphite film is controlled. By using, during the re-forming process, a plurality of inner cores having respective different surface states, it is possible to produce a graphite film having two or more sag forms which have respective effects.