There is provided a PTC device having a sufficient function to detect the possibility of the substrate reaching an extraordinary high temperature more rapidly, and prevent the substrate from reaching such an extraordinary high temperature beforehand. The PTC device 10 includes a layered support 14 that functions as a heat transfer medium and a polymer PTC element 12 disposed thereon wherein the polymer PTC element is disposed on one surface 15 of the layered support (in a thermally connected condition) and the polymer PTC element and the layered support are molded in a resin such that the other surface 15′ of the layered support is exposed.