1. An image forming apparatus for printing a display image serving as a printing target for display on paper with color erasable material, comprising: a printing surface mode determination section configured to determine whether or not a printing surface of the display image is simplex printing; a printer configured to print the display image on a first surface of paper in a case of simplex printing; a curl suppression image determination section configured to determine, in simplex printing case, a printing position and a printing pattern of a curl suppression image for suppressing a curl of the paper caused by the display image based on an analysis result of a display image analysis section which analyzes a printing range and a density of the display image; and a curl-preventive image addition setting section configured to set image information of the printing position and the printing pattern of the curl suppression image which is determined by the curl suppression image determination section and is supposed to be printed on a second surface of the paper with color erasable material by the printer.