The present invention addresses the problem of preventing fusing and rippling of a carbonaceous film in a method for manufacturing a long (rolled-up) carbonaceous film via polymer thermal decomposition. A carbonaceous-film manufacturing method, including a step in which a rolled-up polymer film is heat-treated, that is characterized in that said polymer film is heat-treated after being rolled up such that at a temperature less than the temperature at which the polymer film begins to undergo thermal decomposition, there is a space inside a cross-sectional circle (50% cross-sectional circle), said circle being centered on the center of the roll of polymer film and passing through the point 50% down the length of the polymer film from the inside end thereof, and the area of the space inside the 50% cross-sectional circle constitutes at least 25% of the area of the 50% cross-sectional circle. The existence of a space between a core and the innermost surface of the roll of polymer film is particularly effective with respect to the abovementioned problem.