PURPOSE: To make it possible to melt an oil or fat by hot air under an easy operational condition without bringing a large amount of heat loss, by a method wherein two kinds of oils or fats having different melting temperatures are respectively introduced into a high temp. and a low temp. heating chambers and hot air is appropriately recirculated between one hot air generator and the heating chambers.

CONSTITUTION: One air supply duct 3 from the hot air outlet 2 of a hot air generator 1 is connected to a high temp. heating chamber 4 and the other air supply duct 5 thereof to a low temp. heating chamber 6 and hot air is ejected from respective hot air supply ports 7, 8 to heat coils or fats 9, 10 in containers. Subsequently, respective exhaust airs are introduced into the suction port 5 of the generator 1 from exhaust ports 11, 12 through recirculation ducts 13, 14. A thermostat 16 is attached to a heating chamber 4 and, when the temp. therein reaches a definite temp. or more, the operation of a burner 17 is stopped. In addition, a common shaft 18 is provided to the ducts 5, 14 and dampers 19, 20 are attached to the common shaft 18 and, when the temp. of a heating chamber 6 reaches a set temp. or more, the dampers 19, 20 are cooperated through a motor cylinder 22 by a thermostat 21 to block hot air.