PURPOSE: To heat a work in relatively short time to specific temp. and to effectively dissolve ununiformity of temp. by making up a heating oven for heating the work, which is communicated with generating source of hot air and providing means for generating far infrared radiation to the wall of the heating oven.

CONSTITUTION: The work to be coated is transported to the heating oven 2 by loading on each of the transporting conveyers 19a,b. While, in the heating device, the burner 11 is fired and the hot air blows from ejector 7 and flows again into the upper duct 3 successively passing damper 17, heating oven 2 and hot air passing port 20 in the center part when the recycle fun 8 starts to rotate by driving the motor 13 and heats the work during passing the heating oven 2. The hot air evenly and uniformly heats the work because it can blow even into the interstices of the work. And, the feeding work in said work is smoothly executed because of unnecessary to control the attitude.