To obtain a heating furnace enabling a blow-out temperature of hot air to reach a set temperature for an object to be heated in a short time.

In the heating furnace for sending hot air into a furnace body 2 through a duct 3 to heat the object to be heated by hot air blown out from the furnace body 2, a heating or cooling means 13 for raising or lowering the temperature of the duct 3 and/or the furnace body 2 is provided in the duct 3 and/or the furnace body 2. Thus, when the set temperature for heating the object to be heated is changed, temperatures of the duct 3 and the furnace body 2 are raised or lowered by heating or cooling by the heating and/or cooling means 13 to rapidly make the temperature of the duct 3 and the furnace body 2 approximately equal to the set temperature for heating the object to be heated so as to suppress thermal effects of the duct 3 and/or the furnace body 2 with respect to the heat of hot air passing through the inside of the duct 3 and the furnace body 2.