Heat treatment apparatus

The present invention provides a heat treatment apparatus. The heat treatment apparatus is an IR (infrared radiation) furnace (10). The IR furnace (10) comprises a furnace body (12) and a door (20). The furnace body (12) is provided with a furnace opening which is used for conveying a workpiece (15) in and out. The furnace body (12) is provided with a first sealing part (40) which surrounds the furnace opening. The door (20) is provided with a second sealing part (30) at a position corresponding with the first sealing part (40). The door (20) can close the furnace opening air-tightly through the first sealing part (40) and the second sealing part (30). The first sealing part (40) comprises the following components: a first resin component (42) with heat insulating performance and elasticity; and a resin sheet (44) which covers the first resin component (42) and has high heat resistance. The second sealing part (30) is provided with a plate-shaped second resin component (32) with high heat resistance.