An image reading device, comprising: a reading unit including: a light source to emit light including visible light and invisible light to a passage area through which an object passes; and an imaging device to capture reflected light of the light emitted from the light source to generate a visible image and an invisible image, the imaging device including a plurality of pixels arranged in one direction; a background member disposed opposite the light source across the passage area, the background member having invisible marks identifiable as invisible images by the imaging device, the invisible marks being figures arranged at a predetermined interval in the one direction on the background member; a detection unit to detect a change in an image characteristic due to a change in an optical characteristic of the reading unit, in the invisible images obtained by capturing of the invisible marks; and a correction unit to determine a correction amount of an image characteristic to be used for correcting an image of the object generated by the imaging device, based on the change in the image characteristic detected by the detection unit, and correct the image characteristic based on the correction amount determined, wherein the detection unit is configured to detect, as the change in the image characteristic, a change rate of an interval between the invisible images with respect to the interval between the predetermined invisible marks arranged in the one direction, characterized by a holder to hold a relation between the change rate and the correction amount of the visible image of the object, in correspondence with each of a plurality of positions in the one direction, wherein the correction unit uses the correction amount held in the holder in correspondence with the change rate for each of the plurality of positions, to determine the correction amount of the image characteristic used for correcting each pixel of the visible image of the object. a reading unit including: a light source to emit light including visible light and invisible light to a passage area through which an object passes; and an imaging device to capture reflected light of the light emitted from the light source to generate a visible image and an invisible image, the imaging device including a plurality of pixels arranged in one direction; a light source to emit light including visible light and invisible light to a passage area through which an object passes; and an imaging device to capture reflected light of the light emitted from the light source to generate a visible image and an invisible image, the imaging device including a plurality of pixels arranged in one direction; a background member disposed opposite the light source across the passage area, the background member having invisible marks identifiable as invisible images by the imaging device, the invisible marks being figures arranged at a predetermined interval in the one direction on the background member; a detection unit to detect a change in an image characteristic due to a change in an optical characteristic of the reading unit, in the invisible images obtained by capturing of the invisible marks; and a correction unit to determine a correction amount of an image characteristic to be used for correcting an image of the object generated by the imaging device, based on the change in the image characteristic detected by the detection unit, and correct the image characteristic based on the correction amount determined, wherein the detection unit is configured to detect, as the change in the image characteristic, a change rate of an interval between the invisible images with respect to the interval between the predetermined invisible marks arranged in the one direction, characterized by a holder to hold a relation between the change rate and the correction amount of the visible image of the object, in correspondence with each of a plurality of positions in the one direction, wherein the correction unit uses the correction amount held in the holder in correspondence with the change rate for each of the plurality of positions, to determine the correction amount of the image characteristic used for correcting each pixel of the visible image of the object.