PURPOSE: To detect an original and its width accurately at low cost through a small-sized constitution, by providing a solid-state image pickup element with two couples of sensers, and deciding the presence of the original and its size on the basis of their outputs.

CONSTITUTION: Original sensors 9a and 9b are provided near the solid state image pickup device 6 and original sensors 11a and 11b are provided inside of it; they correspond to the widths of sizes B4 and A4. Further, a back plate 3 facing the read end of an optical fiber 4 is painted in black into a beltlike shape at part of the white ground, and this black part 16 is arranged corresponding to the fiber read end extending from the sensors 9a and 11b. Then, the sensors 9a and 9b correspond to the white ground, so the presence of the original is detected regardless of whether the original is white or black. An original of size B4 is detected by all the sensors, but that of size A is not detected by the sensors 9a and 9b. Thus, the original size is identified.