Heatable sheet assembly

A heatable sheet assembly comprising a sheet to be electrically heated, said sheet being selected from the group consisting of a sheet of carbon fibers and pulp produced by paper making technique, and a sheet of carbon fibers and pulp produced by paper making technique and impregnated with a resin, electrically conductive metal foils applied to both surfaces of said sheet and an electrical terminal attached to each of said metal foils, said sheet of carbon fibers and pulp containing at least carbon fibers of a first group having a length of not less than 3 mm and less than 5 mm and carbon fibers of a second group having a length of longer than 5 mm and not longer than 10 mm, and at least one of said metal foils having a multiplicity of through-holes.