A method of manufacturing an electrical insulation film includes (i) forming an R film containing at least one rare earth element R selected from the group including Sc, Y, La, Gd, Dy, Ho, Er, Tm, and Lu on at least a portion of a surface of a metal substrate where an electrical insulation property is needed, (ii) hydrogenating the R film under an inert gas atmosphere, which contains a hydrogen gas, to form an RH2 film; and (iii) oxidizing the RH2 film to form an R2O3 film.