A coated film drying furnace for drying a coated film inside a furnace body by conveying the coated film therein, the coated film having an absorption spectrum for electromagnetic waves of 3.5 μm or less and having hydrogen bonds, such as an electrode coated film for lithium ion battery. Infrared heaters provided inside a furnace body have outer circumferences of filaments concentrically covered by tubes that function as a low pass filter, and have a structure in which a fluid flow passage is formed at 16 between the plurality of tubes. Due to this, a temperature rise in the furnace is controlled so as to prevent explosion of an organic solvent vapor, and the coated film is efficiently heated and dried by intensively radiating near infrared rays of 3.5 μm or less that have superior ability to cut off the intermolecular hydrogen bonds onto a work.