When copying an object that has faded markings of color fadable toner and is printed with the color fadable toner, a threshold value changing key is displayed on a liquid crystal display of an operation panel to be pressed down. A main CPU sets a threshold value 1a and a threshold value 2a in an image processing unit upon detecting the threshold value changing key displayed on the liquid crystal display of the operation panel via a touch panel. The image processing unit eliminates a background image by using the set threshold value 1a and threshold value 2a, thereby providing dark printing with an excellent image.