The present invention provides a method for manufacturing a film for a film capacitor making it possible to produce a film for a film capacitor which has a thickness of 10 μm or less and which is excellent in a heat resistance and a voltage resistance at a high thickness accuracy by using a polyetherimide resin and provides as well a film for a film capacitor. The above manufacturing method comprises the steps of: feeding a molding material 1 containing a polyetherimide resin into an extruding machine 10, extruding a film 50 for a film capacitor immediately downward from a lip part 21 at a tip of a T dice 20 thereof, interposing the film 50 for a film capacitor between a pressing roll 31 and a cooling roll 33 to cool it and winding up the cooled film 50 for a film capacitor having a thickness of 10 μm or less on a winding equipment 40, wherein assuming that a shear rate of the molten molding material 1 in the lip part 21 of the T dice 20 is set to γ [/s] and that a circumferential speed of the cooling roll 33 is set to V [m/s], a ratio V/γ [m] of a circumferential speed V of the cooling roll 33 to a shear rate γ of the molding material 1 falls in a range of 3.0×10−2 to 90×10−2 [m].