To suppress generation of cyanogen gas with a simple structure even when nitrogen gas is filled in the whole of a furnace body.

This graphite heating furnace 100 is provided with: a nitrogen gas supply part 8 for supplying nitrogen gas into the furnace body 6; an exhaust part 9 for exhausting in-furnace-body gas in the furnace body 6 to the outside of the furnace body 6; and gaps 6a and 6b as discharge parts for discharging the in-furnace-body gas to the outside of the furnace body 6. The dew-point temperature of the nitrogen gas supplied into the furnace body 6 is below -80°C; and the pressure in the furnace body 6 is set above 140 Pa with respect to the atmospheric pressure outside the furnace body 6.

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