Abstract: A paper sheet identification device that detects a stain on a paper sheet and identifies the stained condition of the paper sheet includes an area memory (12) that stores therein in advance an area where a stain is to be detected on the paper sheet as a target detection area, a pixel number memory (11) that stores therein in advance the number of pixels of an image printed on the target detection area as the reference number of pixels used as a reference value when being compared, an image reading unit (13) that, based on the target detection area stored in the area memory, reads an image on the target detection area from the paper sheet, a pixel-number detection unit (14) that detects the number of pixels in the image read by the image reading unit as the number of read pixels, and a calculation unit (15) that calculates a stain value that indicates a stained condition on the target detection area of the paper sheet, by comparing the number of read pixels detected by the pixel-number detection unit with the

Abstract: A paper sheet recognition apparatus includes a sensor that measures feature amounts of a paper sheet; a recognition unit that recognizes whether the paper sheet is genuine or counterfeit, and fit or unfit, based on the feature amount; a memory unit that stores therein a plurality of pieces of different category classification pattern information prepared for each category for classifying the paper sheets into a plurality of categories, which is obtained by combining the feature amounts; and a category determining unit that determines a category of the recognized paper sheet using a recognition result in the recognition unit and the category classification pattern information.