PURPOSE: To carry out energy saving with throughness by contriving highly efficient recovery of exhaust heat, by a method wherein after exhaust gas from a drying oven has been used for preheating of combustion air it is lod further to an air conditioner necessitating a heat source of a low temperature.

CONSTITUTION: This exhaust heat recovery system is a thing obtained by combining so that exhaust gas, which has been exhausted outdoors by only preheating fresh air necessary for combustion of a gas burner 2 which is additional equipment of an oven by making use of a heat exchanger 8, is introduced into a low-temperature heat exchanger 11 and the open air to be supplied to an air conditioner 17 is exhausted outdoors after it has been preheated. Preheating of the open air to be introduced into the air conditioner 17 is done by making use of the exhaust gas obtained after it has been used for preheating of combustion air of the oven, in a jungstrom air preheater 11. As the air conditioner 17 for a working area is a device controlled to the extent of 18W25°C throughout the year, even if a heat source is the exhaust gas of a comparatively low temperature (about 80°C), heat exchanger of the same with the open air becomes effective.