PURPOSE: To completely prevent the generation of reading failure and a paper jamming, to realize high reliability and to attain the miniaturization of a device by projecting a holding part holding the original platen of the casing of a sensor upward from the face of the original platen at an original entrance side and retreating it downward at an original exit side.

CONSTITUTION: The original platen holding part 9f of the original entrance side of a casing 9a has a structure protruded by α upward to the face of the original platen 9d and the tip of a sent original is guided on the original platen 9d smoothly without abutting on the edge part of the original platen 9d. Besides, the original platen holding part 9g of an original exit side has the structure retreated by β downward from the face of the original platen 9d and an original after picture reading is sent to paper ejecting rollers 11 and 12 without abutting on the inner wall face of the original platen holding part 9g. Thus, not only the device can be miniaturized but also the generation of a paper jamming owing to the dislocation of an original guiding member and the paper jamming owing to the breaking down of the original can be prevented.