An image forming apparatus includes an apparatus main body and an original reading device disposed on top of the apparatus main body. A sheet supply cassette, a sheet discharge tray, an original feed tray, and the original discharge tray are oriented such that their lengthwise directions are aligned with the first horizontal direction, and are arranged to overlap with one another in the vertical direction. A pair of side walls is disposed at both widthwise ends of the sheet supply cassette, the sheet discharge tray, the original feed tray, and the original discharge tray. The both widthwise ends of these components are formed as edge portions. The pair of side walls covers an entire length of each of the edge portions, thereby supporting all of the sheet supply cassette, the sheet discharge tray, the original feed tray, and the original discharge tray.