An image forming apparatus including a sheet feed cassette to hold a stack of recording media, a cover detachably attachable to the sheet feed cassette to cover an opening of the sheet feed cassette through which the recording media are supplied, an image forming part to form images on the recording media, and a discharge tray having a top surface on which the recording media discharged from the image forming apparatus after image formation are stacked. The sheet feed cassette is disposed below the discharge tray and is contractibly extendable, protruding outwardly from the image forming apparatus to accommodate large-sized recording media in its extended state. The cover includes a displaceable discharge auxiliary member slidable against the cover so as to be flush with the top surface of the discharge tray and detachably attachable to the sheet feed cassette together with the cover.