To provide a tunnel oven which a countermeasure to global warming, improving hygiene and saving energy are performed in carrying out baking treatment during moving a material over a conveyor of the oven.

This tunnel oven 10 is composed by installing heating devices 13 of a heating furnace 35 for producing hot air and a heating duct 40 arranged along a transporting passage for the material 1 to be baked so that the hot air produced with the heating furnace 35 is passed through the heating duct 40 and returned to the heating furnace 35 in the tunnel oven composed by baking the material 1 to be baked with the heating devices 13 arranged along a transporting passage of the material 1 to be baked in the process for transporting the material 1 to be baked in the interior of the oven body 11 with a transporting device 12. Thereby, the tunnel oven is composed so as to circulate the hot air between the heating furnace 35 and the heating duct 40. As a result, the thermal efficiency of the tunnel oven 10 can be improved.