A treatment instrument including a heat transmitter that includes a treating surface and an installation surface, a substrate attached to the installation surface, and a heat generator formed on a surface of the substrate. The substrate surface and heat generator together form an uneven surface. First and second adhesion layers formed of a material having thermal conductivity and electrical insulation are provided between the installation surface and the substrate. The first adhesion layer is in close contact with the installation surface, and the second adhesion layer is in close contact with the heat generator and the substrate surface. The second adhesion layer is inserted into a recess in the uneven surface formed by the heat generator on substrate surface so as to increase the contact area between the second adhesion layer and the uneven surface.
