PURPOSE: To enable quick heat treatment of coiled objects to be treated to excellent quality in a short period by holding coils loosely wound to form spaces therebetween and imposing the coils in this state on a plenum chamber having many gas ejection ports at the time of subjecting the coiled objects to be treated to a heat treatment such as heating and cooling.

CONSTITUTION: Metallic or nonmetallic sheet-like stocks 25 are loosely coiled W so as to form the spaces 26 and are imposed on the plenum chamber 17 in a furnace shell 10 lined with a heat insulating material 13. The many gas ejection nozzles 27 are formed to face the spaces 26 of the coils W in the plenum chamber 17. The air in the spaces 26 of the coils W and the coil, etc., on the surfaces of the stocks 25 are discharged and cleaned by evacuating the inside of the furnace 12 with a vacuum pump 29 and operating heaters 16, 18. A high-temp. atmosphere is simultaneously circulated from the gas ejection nozzles 27 of the plenum chamber 17 through the spaces 26 of the coils by a circulation fan 23, by which the coils are uniformly heated. The heaters 16, 18 are stopped and a cooler 29 is lowered into a wind box 19 at the time of cooling. The cooled atmosphere gas is circulated by the fan 23 in the same manner as in the heating so that the coils are uniformly cooled at a high speed.