A continuous heat-treating furnace comprises, a housing structure having an entrance and an exit defined at its opposite ends, respectively, and also having defined therein a preheating zone adjacent the entrance, a cooling zone adjacent the exit and a high temperature zone intermediate between the preheating and cooling zones, a recirculating duct fluid-connecting a portion of the housing structure in register with the preheating zone to another portion of the housing structure in register with the cooling zone, and a blower for forcibly drawing gas inside the preheating zone and directing it into the cooling zone through the recirculating duct.