An image reading device includes a light source, a reading unit to convert received light to image data, a correction unit to correct the image data based on correction data, a storing unit storing the correction data, an illumination target switch unit to switch an illumination target between a read position and a reference position, a reflector reflecting light, a judgment unit to judge whether the image data outputted by the reading unit at the read position satisfies a predetermined condition, a correction data determination unit to determine the correction data in response to a fact that the illumination target of the light source is switched to the reference position, and a correction data update unit to store the correction data in the correction data storing unit. The illumination target switch unit switches the illumination target to the reference position if the image data satisfies the predetermined condition.