PURPOSE: To save the unit of a fuel source for heating in a baking oven, by condensing and recovering the gas of a vaporized solvent from the baking oven with a coolant, and using the recovered solvent as a heating source for the baking oven.

CONSTITUTION: The gas of a vaporized solvent in a paint-baking oven 1 is sucked through an exhaust conduit 4 at the inlet side of the oven by a circulating fan 5. The major part of the exhaust gas is introduced into an oven 6 for heating circulating gas, while the residual circulating gas is introduced into a means 7 for recovering a solvent. In the means 7, said gas is cooled and condensed with liquid nitrogen from a tank 8. Thus, the unit of a fuel source assigned to heating in the baking oven is sharply reduced, and the work is performed economically.