To minimize a heating part.

In a cautery probe 4 constructed of a heating element 14 arranged inside a cap 15, an thermally insulative structure reducing heat conduction from the heating element 14 to a part of the outside surface of a cautery probe 4 is constructed. As the thermally insulative structure, a part of the cap 15 is constructed of a highly thermally insulative material, so that a thermally insulative part 17 is distinguished from a cautery part 16 constructed of a highly thermally conductive material.