A circulation channel circularly supplying air heated by a burner is connected to a drying chamber into which a painted workpiece is supplied. The circulation channel includes a flame holding cylinder surrounding a flame of the burner and a casing surrounding the flame holding cylinder from outside and protrudes further than the flame holding cylinder toward a front end side, opposite to a side of the burner, of the flame holding cylinder. The casing includes a low temperature air inlet port that introduces low temperature air from outside into the casing, an exhaust port that exhausts high temperature air heated by the burner and the low temperature air to the circulation channel, and a mixing mechanism that is formed in the casing and mixes the high temperature air and the low temperature air before the high temperature air and the low temperature air are exhausted from the exhaust port.