Abstract: A sheet paper identification apparatus and method for stably identifying a sheet paper while preventing erroneous identification caused by dust adhered to an imaging section and caused by fluctuation in illumination brightness. An imaging section (7) images the interior of the imaging section (7) before a sheet paper is fed to capture image data on an image showing no sheet paper. When a sheet paper is fed into the imaging section (7), the imaging section (7) images the sheet paper and captures image data on an image showing a sheet paper. An image data analyzing section (8) creates a density histogram of the image showing no sheet paper from the image data on the image showing no sheet paper and detects dust adhered to the imaging section (7) on the basis of the density histogram. If the amount of particles exceeds a reference value, the image data analyzing section (8) sends a report about the abnormality of the imaging section (7) to a control section (2).