Provided is a method of producing a graphite film having a high thermal diffusivity, the method including heat-treating, at a temperature of not lower than 2,400° C., a polyimide film or a carbonized film obtained by carbonizing the polyimide film, the polyimide film (i) having a thickness of not less than 34 μm and not more than 42 μm and a birefringence of not less than 0.1000 and (ii) being obtained with use of (a) an acid dianhydride component containing not less than 70 mol % of PMDA and (b) a diamine component containing not less than 70 mol % of ODA.