PURPOSE: To enable the application of a burn trace on a food, and adjustment of heating and heat radiation by laminating a thin paper layer on the exothermic layer or heat resisting sheet side of a heat resisting sheet, and further laminating a thick sheet layer having many holes onto the aforesaid thin paper layer.
CONSTITUTION: A thin sheet layer 3 comprising high quality paper having weight of 15 to 200g/mm 2 is pasted to the side of a heat resisting sheet 2 of the laminate of an exothermic layer 1 and the heat resisting sheet 2 via a heat resisting adhesive layer 6 made of an urethane adhesive, thereby constituting an exothermic material body. A paper layer 4 comprising 0.3 to 2mm thickness cardboard has many circular holes 5 over the entire surface thereof and the numerical aperture of the holes 5 is set at 3 to 80%. The aforesaid paper layer 4 is pasted to the side of the thin paper layer 3 of the exothermic material body via a heat resisting adhesive layer 7 made of a urethane adhesive, thereby forming an exothermic material for a microwave oven. This exothermic material is placed within a microwave oven and a food, for example, a rice cake is placed thereon for heating and drying. Then, it is ensured to apply a trace of burn on the food. Also, the thickness of the thick paper layer 4 and the numerical aperture of the holes 5 can freely be selected and set, thereby enabling the arbitrary adjustment of heating and heat radiation.