To provide a heat treatment method in a fluidized bed type continuous heat treatment furnace, with which the fluidity of heat medium powder can be uniformized in the upper side surface and the lower side surface of a metallic material to be heat treated and the quality of the metallic material after executing the heat treatment by uniformly heating can be improved.

A fluidized bed type continuous heat treatment furnace for executing the heat treatment of a metallic material, is provided with a retort 1 for filling heat medium powder, a heating heater chamber 7 disposed at the outer periphery of the retort, a dispersion plate 4 disposed at the bottom part of the retort, an atmospheric gas supplying hole enabling the supply of the atmospheric gas, an atmospheric gas exhaust hole 3 and a metallic material inlet 5 and a metallic material outlet 5' which are disposed at both sides along the center axis of the furnace and can pass through the metallic material 9 to be heat treated. In such a case, in addition to the atmospheric gas supplied from the dispersion plate arranged at the lower part side of the furnace and also, the gas supplied from plural pieces of atmospheric gas supplying tubes 8 disposed in the retort is fed to the upper surface side of the metallic material to be heat treated passing through the furnace.