An image forming apparatus including an image forming unit, a main body including a first discharge tray configured to receive a sheet conveyed out from the image forming unit, and a resin frame, the main body being configured to support a sheet discharge unit attached thereto, the sheet discharge unit including a second discharge tray configured to receive a sheet conveyed out of the main body through the image forming unit, and an insertion member, a metal bracket attached to the frame, the bracket having an opening into which the insertion member of the sheet discharge unit is inserted when the sheet discharge unit is attached to the main body.