To minimize a gas exhaust piping system and to prevent such trouble as vacuum leakage by removing and recovering wax stuck to the inner part of the gas exhaust piping in the gas exhaust piping system at the time of continuous operation of a vacuum sintering furnace.

The gas exhaust piping 5 from the sintering furnace 6 to the wax traps 1a, 1b is divided into two to form Y-shape type gas exhaust pipings 5a, 5b, and the wax traps 1a, 1b are alternately regenerated and the continuous driving of the apparatus can be executed. Further, an upper jacket 10 and a lower jacket 11 are arranged on the outer periphery of the gas exhaust piping 5a, 5b to flow warm water, etc., and the deposit of the wax 9 is not developed in the inner parts of the gas exhaust pipings 5a, 5b and recovered in a wax storing part 4. In this result, the clogging of valves 3a, 3b for feeding wax gas into the wax traps 1a, 1b are not developed and such trouble as vacuum leakage is prevented.