To provide a heat treatment furnace which can execute the heat treatment in a good energy efficiency and at a low cost.
A holding chamber 5 for holding a material to be treated, is arranged. Then, a hot blast generating chamber 1 freely generating the hot blast is arranged, and the hot blast generating chamber 1 and the holding chamber 5 are connected through a gas sucking passage 4 for supplying the hot blast generated in the hot blast generating chamber 1 into the holding chamber 5. A gas exhaust passage 8 for exhausting the hot blast passed through the holding chamber 5 from this chamber to the outside of the chamber, is arranged, and in the hot blast generating chamber 1, an electric heater 2 and a combustion type gas heater 3 are arranged. Further, a blasting means 6 for blasting the gas heated with at least one side of both heaters 2, 3 into the holding chamber 5 through the gas sucking passage 4, is arranged. An operating device 7 for freely operating to separately change into the working state and the work- stopping state to the electric heater 2 and the combustion type gas heater 3, is arranged.
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