paper feeding roller for feeding an original to a reading position p1 the reference numeral 2 denotes a paper feeding pinch roller the reference numeral 3 designates a paper discharging roller for discharging the read original the reference numeral 4 denotes a paper discharging pinch roller the reference numeral 5 designates an upper original guide forming the upper portion of an original conveying route the reference numeral 6 denotes a lower original guide as a guide member forming the lower portion of the original conveying route the reference numeral 7 designates the body frame of the image reading apparatus and the reference numeral 8 denotes an original keeping plate for preventing the floating of the original at the reading position p1 the reference character 10a designates a light source for illuminating the read surface of the original the reference character 10b denotes an optical sensor as photoelectric converting means for converting the image information of the original into an electrical signal and the reference numeral 10c designates a selfoc lens registered trademark nippon plate glass co ltd as imaging means for imaging the image information of the original illuminated by the light source 10a on the optical sensor 10b the reference character 10d denotes cover glass as a transparent member for guiding the original near the reading position p1 and the cover glass 10d covers the opening portion 6b of the lower original guide 6 the reference character 10e designates a sensor chassis as a holding member for positioning and fixing the light source 10a the optical sensor 10b and the selfoc lens 10c the lower original guide 6 is provided with an opening portion a hollow portion 6b near the reading position p1 and is provided with a mounting portion 6a for mounting and fixing.