An image forming apparatus has a main body with a casing and performs an image forming operation. A sheet receiving surface constitutes part of the casing and can receive a sheet discharged after an image forming process is performed. A window is provided on the sheet receiving surface for enabling part of the interior of the main body to be seen. An auxiliary tray is attached to the sheet receiving surface and is displaceable between an unfolded position to auxiliary support a discharged sheet and an accommodated position to be accommodated in the sheet receiving surface. The window is at a bottom of a recess formed by recessing a part of the sheet receiving surface. The auxiliary tray is accommodated in the recess when at the accommodated position and includes a transparent portion for ensuring visibility of the window.