An image reading apparatus includes: three line sensors mutually spaced in a sub scanning direction; a platen arranged between the original and the three line sensors; a mover moving the platen relative to the three line sensors at a rate relative to the three line sensors, the rate being different from that of the original relative to the three line sensors; a lightness difference detector extracting a feature pixel having a predetermined feature from each of three data output from the three line sensors; and NOR and AND devices comparing the three data corresponding to a single location on the original to detect the feature pixel extracted from one of the three data, as a noise pixel if the feature pixel is not a feature pixel for the other data.