An image forming apparatus includes a plurality of heater elements arranged in a direction perpendicular to a sheet transport direction to heat the sheet, a plurality of temperature sensors, each of which is configured to detect a temperature of one of the heater elements, and a controller configured to control each of the sensors to detect a first temperature before the sheet is passed by the corresponding heater element and a second temperature of the heater element after the sheet is passed by the corresponding heater element, and determine one or more of the heater elements to be energized based on the first temperatures and the second temperatures detected by the sensors.