PURPOSE: To prevent drop in radiation effect and attempt increase in thermal efficiency by utilizing as a heat source a far infrared ray emitting body which is placed above a cooked object inserted in a cooking tank with a specified distance from the object.

CONSTITUTION: A cooked body 5 in a cooking tank 1 is heated through the cooking tank 1 and food oil 3 by a gas burner and also heated by far infrared rays radiated from a far infrared emitting body 2. The heat from the gas burner 4 is transferred to the cooked object 5 with the food oil 3 as a heating medium. Because the far infrared emitting body 2 does not receive heat from the cooking tank 1, the heat quantity supplied to the far infrared emitting body 2 by the cooking gas which stays in the bottom section of the cooking tank 1 does not decrease. Further, because the far infrared emitting body 2 is placed opposite to the mesh belt conveyor 6 with respect to the cooked body 5, part of the radiated far infrared rays are reflected by the conveyor belt and reaches the under-side of the cooked body 5, so that heating is made on both upper and lower faces of the cooking body 5.