To reliably suppress the amount of malodorous gas or the like leaking outside from a coating drying furnace for drying an object coated material at low costs.

The coating drying furnace 1 for drying an object coated material while transporting the object coated material comprises a first and a second detectors 47 and 49 installed in both inlet and outlet sides for detecting the gas flowing-out state to the outside of the drying furnace 1, a first discharge path 31 for taking out the furnace inside gas through the inlet part of the drying furnace 1, a hot air pushing nozzle 53 for jetting hot air in the outlet part of the drying furnace 1, a first adjustment apparatus 36 for adjusting the amount of discharge in the first discharge path 31, a second adjustment apparatus 73 for adjusting the amount of hot air supply through the hot air pushing nozzle 53, and a control means controlling the first adjustment apparatus 36 and the second adjustment apparatus 73 for increasing the amount of discharge in the first discharge path 31 when the gas flow-out rate in the inlet side is increased based on the detection signals of the first detector 47 and for increasing the amount of hot air through the hot air pushing nozzle 53 when the gas flow-out rate in the outlet side is increased based on the detection signals of the second detector 49.