An image forming apparatus capable of selectively discharging a sheet having an image formed with toner on one surface thereof and a sheet having images formed with toner on both surfaces thereof includes a fixing unit configured to fix a toner image on a sheet, a sheet stacking portion configured to stack sheets each having the toner image fixed thereon, and a control portion configured to control a maximum sheet stacking amount of sheets stacked in the sheet stacking portion. The control portion controls the maximum sheet stacking amount set when sheets, at least one of which has the toner images formed on both surfaces thereof, are stacked to be smaller than the maximum sheet stacking amount set when sheets each having the toner image formed on one surface thereof are stacked.