There is provided a heat processing furnace capable of quickly increasing and decreasing a temperature, while achieving improvement in durability. A heat processing furnace 2 comprises: a processing vessel 3 for accommodating an object to be processed w and performing thereto a heat process; and a cylindrical heater 5 disposed to surround an outer circumference of the processing vessel 3, for heating the object to be processed w. The heater 5 includes a cylindrical heat insulating member 16, and heating resistors 18 arranged along an inner circumferential surface of the heat insulating member 16. Each of the heating resistors 18 is formed of a strip-shaped member that is bent into a waveform having peak portions and trough portions. Pin members 20 are arranged in the heat insulating member 16 at suitable intervals therebetween, the pin members 20 holding the heating resistor 18 such that the heating resistor 18 is movable in a radial direction of the heater.