An image reading apparatus having light emitting unit for irradiating light onto a original, reflected light detector light reflected by the original after the original is irradiated by the light emitting unit, outside light detector disposed in an area outside the area in which light reflected by the original enters the reflected light detector and reflected light correcting unit for correcting detection result data detected the reflected light detector based on outside light detected by the outside light detector. An image reading head having light emitting unit, which irradiates, a original with light, and a plurality of light receiving elements arranged in a row having a length longer than a length of the light emitting unit.