To provide a compact multistage heating furnace which reduces an installation area in a factory.

A multistage heating furnace 100 comprises a plurality of heating furnace units 100-1 to 100-10 piled up in a vertical direction. Each heating furnace unit has: an upper heater 102A and a lower heater 101A which are vertically arranged with a heat insulation material 103A placed in between; a support pipe 104A arranged on one end portion of the upper heater 102A in a manner that horizontally extends; a support pipe 104B arranged on the other end portion of the upper heater 102A in a manner that horizontally extends; and a plurality of workpiece support rods 106 which are installed across the support pipes 104A and 104B. The support pipes 104A and 104B are configured to allow cooling water to flow inside the same.