Provided is an image forming apparatus, including: a heating section; a coil that is opposed to the heating section, for heating the heating section; a core that has a circumferential surface covered with a magnetic shielding plate having different lengths in an axis direction in a plurality of steps according to a position in a circumferential direction; a rotary section for causing the core to rotate; a plurality of temperature sensing elements for sensing temperatures of the heating section; and a control section for controlling a heating width by controlling the rotary section to control a rotation angle of the core, setting the heating width corresponding to a size of a paper sheet at a start of a print job, and setting the heating width wider than at the start of the print job midway through the print job.