A device for making a carbon nanotube film includes a substrate and a catalyst layer on the substrate. The catalyst layer has two substantially parallel sides. The present disclosure also provides a method for making a carbon nanotube film. The catalyst layer is annealed at a high temperature in air. The annealed catalyst layer is heated up to a predetermined reaction temperature in a furnace with a protective gas therein. A carbonaceous gas is supplied into the furnace to grow a carbon nanotube array having two substantially parallel side faces. A carbon nanotube film is drawn from the carbon nanotube array. A drawing direction is substantially parallel to the two substantially parallel side faces of the carbon nanotube array.