The present invention provides a sheet supplying apparatus removably connected to an under side of an image forming apparatus to supply a sheet to the image forming apparatus. The apparatus has a main body connected to the under side of the image forming apparatus, a sheet supporting plate provided within the main body of sheet supplying apparatus to support a sheet, sheet supply rotary member for feeding out the sheet from the sheet supporting plate, a convey unit rotatably supported within the main body of sheet supplying apparatus to supply the sheet fed out by the sheet supply rotary member to a sheet receiving opening provided at a side surface of the image forming apparatus, and a positioning unit for positioning the convey unit in the vicinity of the sheet receiving opening.