To prevent accidental contact with a work, generation of spark, and the like, by providing a heat resistant tubular rigid member made of a carbon fiber reinforced carbon composite material while surrounding the outer circumferential surface of a heater tube, e.g. a radiant tube burner or an electric heater, thereby suppressing deformation of the heater tube.

A heating furnace comprises a heater member 1 suspended from the ceiling part of a furnace body 2 comprising a heat insulating wall wherein a work 3 is heated while being moved through the heating furnace by means of a carrying roller 4. The heater member 1 comprises a bottomed heater tube 5 made of stainless steel or heat resistant cast iron and heat is generated by blowing burner flame into a radiant tube or conducting a resistive heater. Outer circumferential surface of such a heater tube 5 is covered with a tubular rigid member 6 made of a carbon fiber reinforced carbon composite material through a cementation resistant material in order to suppress thermal deformation of the heater tube 5.