This invention relates to an image forming apparatus having a fixing device which pressurizes and heats an unfixed toner image on a paper sheet as the transfer medium to fix the image on the paper sheet as the transfer medium. This image forming apparatus includes a glossiness changing device and/or a fixing condition changing device which changes fixing conditions in accordance with the thickness or thickness information of a paper sheet as the transfer medium, and a control section for changing the output order of fixed images to be printed out. This makes it possible to rearrange a printing order so as to shorten the time required to switch a glossiness or change a fixing condition, thereby greatly improving printing efficiency.