To provide a heat treating furnace capable of providing different mechanical properties to a plurality of workpieces treated in a same furnace.

The fluidized bed heat treating furnace 3 is a furnace wherein granular material is filled in a furnace casing 25, the granular material is fluidized by hot air blown in the furnace casing 25 and a fluidized bed is formed, and the plurality of the workpieces 11 are simultaneously heat-treated in the fluidized bed 13, and includes a positioning means 22 for fixing the plurality of the workpieces 11 in a predetermined position in the furnace casing 25, and a plurality of carrying in/out port opening and closing means for charging the plurality of the workpieces 11 in the predetermined position in the furnace casing 25 and removing.