PURPOSE: To detect the presence or absence of a form with a photodetector by setting a mirror surface or a black surface opposite to the photodetector for character reading and sandwiching a form route.

CONSTITUTION: A character reading photodetector 3 contains a photodetecting element 1 and a lens 2. A mirror surface 11 is set opposite to the photodetector 3 and sandwiching a form route 5 in order to prevent or reduce the light reaching the detector 3 from a light source 4. Thus the light of the source 4 does not reach the surface 11 when the form 8 is not at a reading position B. While the light is reflected on the surface of the form 8 and reaches the element 1 when the form 8 is set at the position B. In this case, a black surface can substitute the mirror surface 11 ensure the same effect.