A soldering apparatus, comprising: - a cooling zone (40, 40A, 40B) configured to cool a board subjected to a soldering process; - an upper vent hole provided above a pair of rails (11L, 11R) configured to transport the board in the cooling zone (40, 40A, 40B); - a lower vent hole provided below the pair of rails (11L, 11R) in the cooling zone (40, 40A, 40B); - an external channel that connects the upper and lower vent holes (44, 45) with each other outside the cooling zone (40, 40A, 40B); - a blower unit that is communicated with the upper vent hole, and configured to cause gas in the external channel to flow through the upper vent hole hole, the cooling zone (40, 40A, 40B), and the lower vent hole in order and return to the external channel; and - a heat exchanger provided in a lower opening linked to the lower vent hole below the pair of rails (11L, 11R), and configured to cool gas passing through the lower opening; characterized by: - a pair of bypass channels (72, 73) provided in parallel to the pair of rails (11L, 11R) on lateral sides of the pair of rails (11L, 11R), and configured: - to draw in gas above the pair of rails (11L, 11R) through inlet ports (72a, 73a), - to let the gas flow through the bypass channels (72, 73), - to discharge the gas through discharge ports (72b, 73b) while bypassing locations of the pair of rails (11L, 11R), and - to thereby deliver the gas to the lower opening; and - a ventilation plate provided in a space formed between the pair of bypass channels (72, 73) below the pair of rails (11L, 11R), and provided with a slit used to send gas below the pair of rails (11L, 11R) to the lower opening. comprising: - a cooling zone (40, 40A, 40B) configured to cool a board subjected to a soldering process; - an upper vent hole provided above a pair of rails (11L, 11R) configured to transport the board in the cooling zone (40, 40A, 40B); - a lower vent hole provided below the pair of rails (11L, 11R) in the cooling zone (40, 40A, 40B); - an external channel that connects the upper and lower vent holes (44, 45) with each other outside the cooling zone (40, 40A, 40B); - a blower unit that is communicated with the upper vent hole, and configured to cause gas in the external channel to flow through the upper vent hole hole, the cooling zone (40, 40A, 40B), and the lower vent hole in order and return to the external channel; and - a heat exchanger provided in a lower opening linked to the lower vent hole below the pair of rails (11L, 11R), and configured to cool gas passing through the lower opening; - a cooling zone (40, 40A, 40B) configured to cool a board subjected to a soldering process; - an upper vent hole provided above a pair of rails (11L, 11R) configured to transport the board in the cooling zone (40, 40A, 40B); - a lower vent hole provided below the pair of rails (11L, 11R) in the cooling zone (40, 40A, 40B); - an external channel that connects the upper and lower vent holes (44, 45) with each other outside the cooling zone (40, 40A, 40B); - a blower unit that is communicated with the upper vent hole, and configured to cause gas in the external channel to flow through the upper vent hole hole, the cooling zone (40, 40A, 40B), and the lower vent hole in order and return to the external channel; and - a heat exchanger provided in a lower opening linked to the lower vent hole below the pair of rails (11L, 11R), and configured to cool gas passing through the lower opening; characterized by: - a pair of bypass channels (72, 73) provided in parallel to the pair of rails (11L, 11R) on lateral sides of the pair of rails (11L, 11R), and configured: - to draw in gas above the pair of rails (11L, 11R) through inlet ports (72a, 73a), - to let the gas flow through the bypass channels (72, 73), - to discharge the gas through discharge ports (72b, 73b) while bypassing locations of the pair of rails (11L, 11R), and - to thereby deliver the gas to the lower opening; and - a ventilation plate provided in a space formed between the pair of bypass channels (72, 73) below the pair of rails (11L, 11R), and provided with a slit used to send gas below the pair of rails (11L, 11R) to the lower opening. - a pair of bypass channels (72, 73) provided in parallel to the pair of rails (11L, 11R) on lateral sides of the pair of rails (11L, 11R), and configured: - to draw in gas above the pair of rails (11L, 11R) through inlet ports (72a, 73a), - to let the gas flow through the bypass channels (72, 73), - to discharge the gas through discharge ports (72b, 73b) while bypassing locations of the pair of rails (11L, 11R), and - to thereby deliver the gas to the lower opening; and - to draw in gas above the pair of rails (11L, 11R) through inlet ports (72a, 73a), - to let the gas flow through the bypass channels (72, 73), - to discharge the gas through discharge ports (72b, 73b) while bypassing locations of the pair of rails (11L, 11R), and - to thereby deliver the gas to the lower opening; and - a ventilation plate provided in a space formed between the pair of bypass channels (72, 73) below the pair of rails (11L, 11R), and provided with a slit used to send gas below the pair of rails (11L, 11R) to the lower opening.