This heating furnace includes a housing having a pair of side walls, a workpiece support material to support a workpiece, a planar heater to heat the workpiece supported by the workpiece support material from above or below, a power feeding device to feed power to the planar heater. The planar heater has a plurality of heating bodies disposed side by side in a conveyance direction and in a left-right direction orthogonal to the conveyance direction in a plan view, the heating bodies each have a heating wire and a sintered body to accommodate the heating wire, include two or more kinds of heating bodies, and include an intermediate heating body alongside which other heating bodies are disposed at both end portions in the left-right direction, and the power feeding device has a feeding unit configured to feed power to each of the heating bodies from the side wall.