An image reading apparatus includes: a light source which irradiates illumination light to a document; an imaging element which images reflected light of the illumination light from the document; a color separator which performs color separation of the illumination light or the reflected light into at least three wavelength ranges including a first wavelength range, a second wavelength ranges and a third wavelength range; a light-receiving element which converts the reflected light imaged by the imaging element into an electrical signal as a document image of the document, for each of the at least three wavelength ranges; and an image processor which classifies the document image on the basis of the electrical signal in the first wavelength range and in the second wavelength range.