The present invention provides a dual transmissive/reflective image scanning apparatus for improving the scanning quality of reflective originals. The present invention includes a slot for selectively accommodating a tray of a first type or a tray of a second type. For reflective scanning, the tray of the first type, which includes a means of transparent material such as glass, is inserted within the slot. For transmissive scanning, the tray of the second type without a means of transparent material may be selectively inserted within the slot. As scanning transparent originals, a light source from the original cover passes directly thought the transparent originals and thus it reduces obstruction that may be caused by a transparent material. Furthermore, either the tray of the first type or the tray of the second type is allowed to be withdrawn from the housing for cleaning greasy dirt or dust deposited on the glass or installing various holders for transparent originals.