To solve a problem in a heating device of a preheating chamber in a vacuum type sintering furnace wherein heating temperature to a treated material is set higher than a set temperature, vapor of fatty or oily material generated from the treated material is decomposed, and the decomposed product adheres to the treated material to increase carbon concentration of sintered product.

The heating device of the vacuum type sintering furnace heats the treated material W with heating sections 52, 54, 56, 58, 60 and 62 disposed in the preheating chamber 14. A pipe is disposed in the preheating chamber 14, a heating medium previously heated to a predetermined temperature is made to flow in the pipe to constitute the heating sections 52, 54, 56, 58, 60 and 62, and the treated material W is heated by heat from the heating medium.