<p>A solder reflow furnace includes piping to supply an inert gas into the furnace to maintain an inert gas atmosphere within the furnace and a cooling zone provided next to a main heating zone. The cooling zone is provided with a gas cooling device in which printed cirtuit boards after soldering are cooled by an inert cooling gas which is in turn cooled indirectly by air outside the furnace so that air is prevented from flowing into the furnace. <IMAGE></p>
