Abstract: An image forming apparatus including a paper cassette loaded with a stack of papers and a paper stacking device for stacking papers carrying images thereon is disclosed. The apparatus has an upper casing part rotatable away from a lower casing part. When the upper casing part is rotated away from the lower casing part, the apparatus successfully prevents the upper casing part from interfering with a tray or similar paper stacking means and prevents papers stacked on the tray from dropping without having its overall length increased. The tray is arranged in the rear portion of the apparatus opposite to the front portion where a control panel is located, thereby reducing the widthwise dimension of the apparatus. Even in such a position, the tray allows papers stacked thereon to be easily picked up.