An image forming apparatus includes an image forming portion capable of forming a toner image on an envelope including a flap; a stacking portion configured to stack the envelope; a fixing portion configured to fix the toner image on the envelope; a display portion configured to display information; and a controller configured to control the display portion so that when the double-side mode in which the images are formed on the double sides of the envelope is selected, a stacking method in which the envelope is stacked on the stacking portion so as to fix the image on a flap-formed side when the envelope first passes through the fixing portion is displayed at the display portion.