PURPOSE: To prevent dropping of the heat transfer converting body due to the crack thereof by a method wherein a part, having smaller sectional coefficient, is provided so as to be extended into a constant direction with respect to the direction of the surface of heat transfer converting body.

CONSTITUTION: The heat transfer converting body 1 is made of ceramics and is formed into a plate having proper length Y, width X and thickness Z while a plurality of grooves, having V-shaped sections, are indented with a given interval so as to be extended into the lengthwise direction Y of the surface of the plate. According to this method, a crack, generated by thermal impulse (spalling), may be generated along a part having the smaller sectional coefficient. Accordingly, dropping of the heat transfer converting body, which is caused by the generation of the crack, may be prevented by mounting the heat transfer converting body in a condition that the part having smaller sectional coefficient is extended into orthogonal direction with respect to the support of the heat transfer converting body.