A heater including a substrate, a first heat generating line provided on the substrate and in a longitudinal direction of the substrate, the first heat generating line being divided into a plurality of heat generating blocks in the longitudinal direction, the plurality of heat generating blocks being controllable independently, and a second heat generating line provided on the substrate and in the longitudinal direction of the substrate, the second heat generating line being divided into a plurality of heat generating blocks in the longitudinal direction, the plurality of heat generating blocks being controllable independently. In the heater, divided positions of the first heat generating line and divided positions of the second heat generating line are different.