An image forming apparatus includes first and second heaters and a controller. The first and second heaters have a same light distribution and heat a roller of an image fixing unit. The second heater generates a less heat amount than the first heater. The controller applies a drive voltage to a heater of the heaters. When a heat amount generated by the second heater has increased to a first threshold value by the controller controlling the drive voltage, the controller switches the drive-voltage-applied heater from the second heater to the first heater. When a heat amount generated by the first heater has decreased to a second threshold value smaller than the first threshold value by the controller controlling the drive voltage, the controller switches the drive-voltage-applied heater from the first heater to the second heater.