PURPOSE: To heat-treat a large number of objects simultaneously and uniformly, thereby forming products of high quality without producing dispersion in the quality thereof, and to perform the treatment in a short time of period while preventing the influence of smog of solvent or the like, which is generated in the heat treatment.

CONSTITUTION: Air of proper temperature is drawn from a heated air source 4 by a blower motor 3 controlled by a controller 5, which air is sent to a blowoff pipe 2 through a flexible hose 8 or the like, thereby blowing off the air from a blowoff port 6. The heated air blown off from the port 6 uniformizes the temperature of an object which is heated by far infrared rays or the like and also heats the object thoroughly.