Composite sheet 11 contacts or is adhered to an external device (not shown), such as a heat generating device and a low temperature device, to be used as a thermally-conductive member for dissipating heat from the external device or for supplying heat to the external device. In order to provide preferable thermal conduction from or to the external device, composite sheet 11 is often used while being adhered to an outer surface of the external device.

2. Method of Producing Composite Sheet

Next, a method of producing composite sheet 11 in accordance with the exemplary embodiment will be described below with reference to FIGS. 2A to 2C. FIGS. 2A to 2C illustrates the method of producing composite sheet 11 in accordance with the exemplary embodiment.

First, as shown in FIG. 2A, a polyimide film is pyrolized to be graphitized, and then, is tanned to obtain thermally-conductive sheet 11 formed of a flexible graphite sheet.

Next, as shown in FIG. 2B, first through holes 15 are formed on thermally-conductive sheet 12 by a punching process with a punch die or by a laser beam processing.