PURPOSE: To detect paper easily by forming at least a part corresponding to an infrared sensor out of a paper guide plate by a member for passing infrared rays and shielding visual light rays.

CONSTITUTION: An original P is fed along a paper guide 11 by rollers 5W7. A transmission type infrared-ray sensor 14 consisting of a light emitting element 12 and a photodetecting element 13 which are oppositely arranged through the plate 11. The plate 11 is formed by a member, e.g. transparent resin mixed with a violet dye, for passing infrared rays and shielding visual light rays. When the original P does not exist, infrared rays radiated from the element 12 are transmitted through the plate 11 and made incident upon the element 13, and when the original P exists, the infrared rays are not made incident upon the element 13, so that the existence of the original P can be detected. Since the late 11 passes the infrared rays and shields the visual light rays, the element 13 does not receive the visual light rays and is prevented from misdetection. Thus, the original P can be detected without interrupting the carrying of the original P.