PURPOSE: To detect the generation of overlap feed to sheet material correctly in a sheet material processing device for taking out sheet material sheet by sheet from a storage part where the sheet material semi-transmitting light at the specified transmittance is stored in the laminated state and conveying the sheet material to a processing part to perform specified processing.

CONSTITUTION: A film conveying passage to a photographing part from a supply magazine 1 with films 2 enclosed therein is provided with a photodiode 21 for emitting infrared rays, and a phototransistor 22 for detecting the infrared rays. The film 2 passes between the photodiode 21 and the phototransistor 22, and the infrared rays of the diode 21 are semi-transmitted through the film 2 at the specified transmittance and received by the transistor 22. The transmission quantity of the infrared rays differs according to the number of films 2 passing between the diodes 21 and transistor 22, so that the infrared ray receiving quantity of the transistor 22 differs, and its output differs. The number of films 2 in passage can be thereby judged from the output of the transistor 22 so as to detect the generation of overlap feed correctly.