To provide a heating furnace which keep the temperature in the furnace always uniform, and maintains uniform heating of an object.

The heating furnace has a hot plate, which has a source of heat, a reflective board, which does not have the source of heat, installed in the opposite side of this hot plate, and a passage formed in between the above hot plate and the reflective board, through which the object passes, and it is composed to heat the object by the above hot plate. In it, preparing a cave to the above reflective board, a temperature control means, which control the temperature of the reflective board by flowing fluid in this cave, is prepared.