The heater device has a sheet shaped main body having a heat generating portion heated by energization and a radiating surface for radiating radiant heat toward a heating object by using heat in the heat generating portion, a plate shaped member arranged on an opposite side with respect to the radiating surface of the main body, and an air layer forming member for forming an air layer between the main body and the plate shaped member arranged on a side opposite to the radiating surface of the main body.