PROBLEM TO BE SOLVED: To improve workability and safety workability with no possibility of lowering performance during work by effectively cooling a heating coil and a high frequency output circuit, and to easily and accurately put a portion of the heating coil on the upper face of a fixed disk hidden by the back face of a waterproof sheet. SOLUTION: The heating coil 1 for generating an induced current to a conductive metal plate B' of a fixed disk plate B, a high frequency oscillating part 2 including a high frequency output circuit or the like for supplying a high frequency current to the heating coil, and a cooling fan 3 are built in one outer case 4, and an air passage 6 is formed inside the outer case so that outside air passes near the heating coil and the high frequency output circuit. A cooling fin 7 with the high frequency output circuit installed is disposed at an intermediate part of the air passage, and a sign 11 for specifying the center of the heating coil is provided at an outer case outer upper face located directly above the heating coil. COPYRIGHT: (C)2004,JPO