In a method for producing a carbonaceous film in which a polymer film is wrapped around a core and is subjected to a heat treatment, material film surfaces during the carbonization step are prevented from fusion, whereby a long carbonaceous having a large area film is obtained.Fusion can be prevented by subjecting a polymer film to a heat treatment under a reduced pressure, and under a reduced pressure while allowing an inert gas to flow. The range of the pressure reduction is preferably −0.08 MPa to −0.01 kPa. It is preferred to carry out carbonization with the pressure reduced in the range of from −0.08 MPa to −0.01 kPa while allowing an inert gas to flow. In addition, the polymer film wrapped around the core is placed in an outer casing, and provided that a value derived by dividing (internal diameter of the outer casing−diameter of the core) by 2 is designated as “a” (mm), and a thickness of wrapping of the polymer film is designated as “b” (mm), a value (b/a) derived by dividing the “b” by the “a” is set to fall within the range of from 0.2 to 0.9.