To solve problems that an amount of oxidation of heat resistant steel used in a kiln under an indirect heating is increased, the steel cannot be used due to the increase of thermal distortion at high temperature exceeding 1100°C, and a large product cannot be manufactured by using ceramics.

A hard fireproof material is formed in a cylindrical steel plate provided with a charging wall and an exhaust wall at the front and rear parts thereof to have a furnace body. On both the walls, a plurality of through holes are opened at positions near the center so as not to come into contact with inner powder to be treated even upon rotation and a rod type silicon carbide heater is mounted. At the central part of the charging wall, a hole is opened and used as an inlet port. At the end of the exhaust wall, the side wall of the cylinder is extended and a hole is opened to be used as an exhaust port. On the outer surface of the furnace body, two tires and sprockets are provided and assembled with four support rollers and two stopper rollers and a rotating speed reducer similarly to a well-known rotary kiln.