An image forming apparatus includes a housing, an image forming unit disposed inside the housing, a discharging portion, a stacking unit and a pressing member. The discharging portion is configured to discharge a sheet medium on which an image is formed by the image forming unit. The stacking unit is configured to stack the sheet medium discharged from the discharging portion. The stacking unit includes a stacking surface portion on which the sheet medium is stacked. The stacking surface portion includes a planar portion formed flat and a protruding portion configured to protrude upwardly from the planar portion. The pressing member is disposed in contact with an upper surface of the sheet medium stacked on the stacking surface portion.