To maintain a firing object at a desirable tap. by forming a tap. gradient in a firing chamber, comparing the actual temp. and theoretical temp. with a temp. sensor built into a firing object transporting device and moving the firing object in a desirable temp. zone.

A firing pedestal 13 is formed of hermetic ceramics and is further advantageously formed of a ceramic type fibrous insulating material fused in quartz glass on the entire flank. A metallic mirror 14 is melted in the upper part thereof to improve heat reflection. The firing object transporting device 15 is moved together with the firing object 16 above the firing pedestal 13. A conduit 10 for a thermoelectric element 17 is arranged at the firing object transporting device 15 and the firing pedestal 13 near the firing object 16 and this thermoelectric element 17 is conducted. The thermoelectric element 17 is connected to a temp. control unit 19. The pulse signal of the unit 19 is transmitted to a lifting device 18. This lifting device 18 lifts the firing object 16 relative to a heater 5, thereby exactly maintaining the firing object at the adequate temp. with slight movement.