The invention relates to a built-in heat-discharging type gas generation device heat treating furnace, which comprises devices such as a material feeding platform, a preheating chamber, a heating chamber, a cooling chamber and a material discharging platform. A mixing combustor of the heat-discharging type gas generation device is built in the preheating chamber (or heating up region) of the heat treating furnace, the heat-discharging gas generation device is used to prepare protective gas which is needed by the heat treating furnace in the heat treating process, the combustor of the heat-discharging gas generation device is directly arranged into the preheating chamber of the heat treating furnace, thus not only can directly prepare protective gas in furnace, but also can directly reclaim large amount of chemical reacting heat which is generated in the process of preparing protective gas, wherein the heat energy which is reclaimed can be used to heat up work-pieces in furnace, therefore the heat treating furnace can reasonably use energy, and has extremely considerable energy-saving effect.