To detoxify a hydrogen gas without using a combustion device and to release it from a soldering device to the outside air.

A nitrogen gas is supplied in an outer tank 4. The outer chamber is provided with a pre-heating chamber 10, a heating exhaust chamber 12 and a cooling chamber 14. These chambers are supplied with a hydrogen gas having a pressure higher than that of the nitrogen gas. A material 1 to be soldered is transported through the pre-heating chamber 10, the heating exhaust chamber 12 and the cooling chamber 14. Solder is pre-heated in the pre-heating chamber 10, and the solder is melted and voids in the molten solder is brokendown by evacuation in the heating exhaust chamber 12. The molten solder is solidified in the cooling chamber 14. The hydrogen gas flown out to the outer tank 4 from the pre-heating chamber 10, the heating exhaust chamber 12 and the cooling chamber 14 is diluted by the nitrogen gas and released from exhaust pipes 8a, 8b to the outside air.