A controller controls power to be supplied to a plurality of heat-generating blocks obtained by dividing a heater in a direction orthogonal to a transport direction for a recording material, and when images formed on a plurality of sheets of the recording material having an equal size are continuously heated, and the controller determines whether each of the heat-generating blocks is a heat-generating block which is passed by the recording material or a heat-generating block which is not passed by the recording material on the basis of a detection temperature by a temperature detecting element when prescribed power is supplied to the heat-generating block and changes a control condition in heating on the basis of the determination.