A heating device includes a belt that rotates in a rotation direction and has a temperature decrease span in an axial direction of the belt, where the belt is susceptible to temperature decrease. A resistive heat generator is disposed opposite the belt. The resistive heat generator heats the belt and extends in the axial direction of the belt. The resistive heat generator includes a primary heat generating portion that generates heat in a first heat generation amount and a secondary heat generating portion that is disposed outside the primary heat generating portion and disposed opposite the temperature decrease span of the belt. The secondary heat generating portion generates heat in a second heat generation amount that is greater than the first heat generation amount of the primary heat generating portion.