An image reading device, comprising: a light source configured to emit light; a reading unit configured to read light reflected from an object and convert the read light to image data; a correction unit (66a, 66b) configured to correct the image data outputted by the reading unit based on correction data; a correction data storing unit configured to store the correction data to be used by the correction unit (66a, 66b); an illumination target switch unit configured to switch an illumination target between a read position (21 a) through which a document passes and a reference position (21 b) different from the read position; a reflector above the read position for reflecting, toward the reading unit, the light emitted to the read position by the light source, when the reading unit is situated beneath the read position; a judgment unit configured to make a judgment as to whether the image data outputted by the reading unit when the illumination target of the light source is at the read position satisfies a predetermined condition; a correction data determination unit configured to determine the correction data based on the image data outputted by the reading unit in response to a fact that the illumination target of the light source is switched to the reference position by the illumination target switch unit; and a correction data update unit configured to store the correction data determined by the correction data determination unit in the correction data storing unit, wherein the illumination target switch unit is configured to switch the illumination target to the reference position in response to the judgment unit judging that the image data satisfies the predetermined condition, further comprising a transparent member which allows the light from the light source to pass therethrough and is located such that the document can be situated thereon, wherein the reflector comprises a pressing member having a function of pressing the document against the transparent member at the read position (21 a) such that the image reading device comprises a component used both as the reflector and the pressing member. a light source configured to emit light; a reading unit configured to read light reflected from an object and convert the read light to image data; a correction unit (66a, 66b) configured to correct the image data outputted by the reading unit based on correction data; a correction data storing unit configured to store the correction data to be used by the correction unit (66a, 66b); an illumination target switch unit configured to switch an illumination target between a read position (21 a) through which a document passes and a reference position (21 b) different from the read position; a reflector above the read position for reflecting, toward the reading unit, the light emitted to the read position by the light source, when the reading unit is situated beneath the read position; a judgment unit configured to make a judgment as to whether the image data outputted by the reading unit when the illumination target of the light source is at the read position satisfies a predetermined condition; a correction data determination unit configured to determine the correction data based on the image data outputted by the reading unit in response to a fact that the illumination target of the light source is switched to the reference position by the illumination target switch unit; and a correction data update unit configured to store the correction data determined by the correction data determination unit in the correction data storing unit, wherein the illumination target switch unit is configured to switch the illumination target to the reference position in response to the judgment unit judging that the image data satisfies the predetermined condition, further comprising a transparent member which allows the light from the light source to pass therethrough and is located such that the document can be situated thereon, wherein the reflector comprises a pressing member having a function of pressing the document against the transparent member at the read position (21 a) such that the image reading device comprises a component used both as the reflector and the pressing member.