A soldering apparatus, comprising: a furnace body including a processing chamber in which boards are processed; a gasket provided at least to a part of the furnace body, and configured to seal the furnace body; characterised in that: the gasket includes a first seal, a second seal that is arranged away from the first seal, a third seal that effects sealing between the first seal and the second seal, and a fourth seal that effects the sealing between the first seal and the second seal and that is arranged away from the third seal, and a sealed space (S1, S2, S3, S4, S5) isolated and distinct from the processing chamber to serve as an independent space, and defined by the furnace body and the gasket; and, in that the sealed space (S1, S2, S3, S4, S5) is defined at least by the furnace body, the first seal, the second seal, the third seal, and the fourth seal, and being further characterised by: a gas supply apparatus configured to supply a first gas into the sealed space (S1, S2, S3, S4, S5); a measuring apparatus configured to measure one of pressure in the sealed space (S1, S2, S3, S4, S5) and concentration of a second gas in the sealed space (S1, S2, S3, S4, S5); and a control apparatus capable of communicating with the measuring apparatus, wherein the control apparatus is configured to determine whether or not the one of the pressure and the concentration received from the measuring apparatus has reached a predetermined threshold. a furnace body including a processing chamber in which boards are processed; a gasket provided at least to a part of the furnace body, and configured to seal the furnace body; provided at least to a part of the furnace body, and configured to seal the furnace body; characterised in that: the gasket includes a first seal, a second seal that is arranged away from the first seal, a third seal that effects sealing between the first seal and the second seal, and a fourth seal that effects the sealing between the first seal and the second seal and that is arranged away from the third seal, and the gasket includes a first seal, a second seal that is arranged away from the first seal, a third seal that effects sealing between the first seal and the second seal, and a fourth seal that effects the sealing between the first seal and the second seal and that is arranged away from the third seal, and a sealed space (S1, S2, S3, S4, S5) isolated and distinct from the processing chamber to serve as an independent space, and defined by the furnace body and the gasket; and, in that the sealed space (S1, S2, S3, S4, S5) is defined at least by the furnace body, the first seal, the second seal, the third seal, and the fourth seal, and being further characterised by: a gas supply apparatus configured to supply a first gas into the sealed space (S1, S2, S3, S4, S5); a measuring apparatus configured to measure one of pressure in the sealed space (S1, S2, S3, S4, S5) and concentration of a second gas in the sealed space (S1, S2, S3, S4, S5); and a control apparatus capable of communicating with the measuring apparatus, wherein the control apparatus is configured to determine whether or not the one of the pressure and the concentration received from the measuring apparatus has reached a predetermined threshold. isolated and distinct from the processing chamber to serve as an independent space, and defined by the furnace body and the gasket; and, in that the sealed space (S1, S2, S3, S4, S5) is defined at least by the furnace body, the first seal, the second seal, the third seal, and the fourth seal, and being further characterised by: a gas supply apparatus configured to supply a first gas into the sealed space (S1, S2, S3, S4, S5); a measuring apparatus configured to measure one of pressure in the sealed space (S1, S2, S3, S4, S5) and concentration of a second gas in the sealed space (S1, S2, S3, S4, S5); and a control apparatus capable of communicating with the measuring apparatus, wherein the control apparatus is configured to determine whether or not the one of the pressure and the concentration received from the measuring apparatus has reached a predetermined threshold. a gas supply apparatus configured to supply a first gas into the sealed space (S1, S2, S3, S4, S5); a measuring apparatus configured to measure one of pressure in the sealed space (S1, S2, S3, S4, S5) and concentration of a second gas in the sealed space (S1, S2, S3, S4, S5); and pressure in the sealed space (S1, S2, S3, S4, S5) and concentration of a second gas in the sealed space (S1, S2, S3, S4, S5); and a control apparatus capable of communicating with the measuring apparatus, wherein the control apparatus is configured to determine whether or not the one of the pressure and the concentration received from the measuring apparatus has reached a predetermined threshold.