In an image forming apparatus including an image heating portion that heats an image formed on a recording material using heat of a heater constituted of a substrate and a plurality of heat generating resistors disposed on the substrate, the plurality of heat generating resistors include (i) a first heat generating resistor that has a first temperature coefficient of resistance, and (ii) a second heat generating resistor that has a second temperature coefficient of resistance which is smaller than the first temperature coefficient of resistance, and heats a second heating region of which width in the longitudinal direction of the substrate is narrower than the first heating region which is heated by the first heat generating resistor, among the plurality of heating regions heated by the plurality of heat generating resistors.