A heating device includes a surface heater unit including a heater portion that generates heat in a region extending in a longitudinal direction, the surface heater unit heating a heating object; a support unit that supports the surface heater unit; and a heat conducting unit disposed in contact with a surface of the surface heater unit at a side opposite to a side adjacent to the heating object in a region between a center of the heater portion in a direction crossing the longitudinal direction and the support unit.