PURPOSE: To provide a paper sheet discriminating device which can detect irregularity in a sheet surface, adhesion of foreign matter such as tape.

CONSTITUTION: A pressing member 4 is provided which presses a paper sheet S, which constitutes a carrier passage with a part of the outer circumference surface side of a columnar or cylindrical guide member 2, and is fed along it, from the top end side against a guide member 2 side in order, and curves a pressed part of the sheet S, and a light source 12 and a light receiving part 8 are disposed fore and aft approximately along the tangential direction of the curved part of the sheet S. Irregularly reflected light due to irregularity, generated when the light emitted from the light source 12 passes through or is reflected by the curved part of the sheet S is detected by the light receiving part 8.