PURPOSE: To easily sinter the wax in a dewaxing gas and to efficiently remove the wax by conducting the dewaxing gas discharged from a sintering furnace to a wax trap and cooling the same with an evaporator for an inert gas to be supplied into the furnace.

CONSTITUTION: The inert gas is supplied from a liquefying storage device 4 through the evaporator 8 disposed in the wax trap 9 into the sintering furnace 1 which heats and calcines a treating material 2 with a heater 3. On the other hand, the dewaxing gas generated in the furnace 1 is passed via a discharge pipe 7 through the above-mentioned wax trap 9 and after the wax W is removed therefrom, the gas is discharged by a vacuum pump 6. The wax W is solidified by the evaporator 8 consisting of a long-sized piping 5 in the wax trap 9 provided with trap pieces 13 on trap plates 12 having vent holes 12a and thereafter, the wax is melted and held by heaters 14, 15 and is discharged via a drain valve 16.