PURPOSE: To enable pure electrical detection of the front/rear sides of a stencil paper through utilization of output signals, by providing means for detecting a section to be detected at a position corresponding to said section when a stencil paper is fed under a normal attitude.

CONSTITUTION: An elongated hole 47 is made at a position separated by 50mm to be left from a center line 46 which is parallel with the moving direction of a mimeographic stencil paper 16a, and when a lug portion 43 is positioned below a photo-coupler 41, the beam is reflected to produce an output signal 'H', while when the elongated hole 47 arrives, the beam is radiated through the elongated hole 47 so as to produce an output signal 'L'. Consequently, when the mimeographic stencil paper 16a is fed under a normal attitude, signals are fed from the photo-coupler 41 in the order of L-H-L-H. When the mimeographic stencil paper 16a is fed while being turned over, the elongated hole 47 is not detected so as to produce signals in the order of L-H-H-H. When the mimeographic stencil paper 16a is not fed, signals are fed in the order of L-L-L-L. A motor 49 for driving a printing plate 2 is rotated only when the output signals are fed in the order of L-H-L-H.