a plurality of sensors positioned at an oblique angle relative to a transporting direction of leaves of paper, the plurality of sensors being arranged in a single row that extends in a direction orthogonal to the transporting direction of the leaves of paper, wherein directions of inclination of the plurality of sensors are all identical, and wherein adjacent sensors are continuous with each other when seen from the transporting direction of the leaves of paper;

a plurality of memory devices that respectively memorize output signals from each of the sensors;

a synthesizing device that synthesizes signals from the memory devices as a continuous signal; and

an identification device that identifies whether or not leaves of paper are authentic based on the signal synthesized by the synthesizing device.