Disclosed herein is a method of manufacturing a composite carbon sheet, including the steps of: mixing 70 parts by weight of a first solution as a dispersant with 30 parts by weight of a second solution as a binder to prepare a third solution; mixing 80˜97 parts by weight of the third solution with 3˜20 parts by weight of any one selected from the group consisting of single-wall carbon nanotubes, double-wall carbon nanotubes, multi-wall carbon nanotubes, carbon nanofibers, carbon nanoparticles, graphene and fullerene to prepare a fourth solution; dispersing the fourth solution to prepare a mixed dispersion solution; and coating an expanded graphite sheet with the mixed dispersion solution. The method is advantageous in that the thermal conductivity of the composite carbon sheet manufactured by this method can be improved, the physical properties thereof can be enhanced, the exfoliation thereof can be prevented, and the tensile strength and tear strength thereof can be improved.