An image reading apparatus is provided that can prevent image streaks due to dirt, stain or the like from being produced in an image of an original that is read while being conveyed. The image reading apparatus (A) includes an ADF (40) having a scanner unit (59) incorporated therein and comprised of a cylinder (60) having an outer peripheral surface thereof on which a plurality of read pixels (61) are arranged in a matrix. In reading an original (D), the scanner unit is rotatably driven in an original conveying direction at a circumferential speed approximately equal to an original conveying speed, and reads image information on the original passing through an image reading position (P1).