The present invention provides an image correcting method and relevant device for file scanning. The scanner includes a casing, a shade, a slide rail and a scanning module. The casing has a transparent platform for fiole to be placed on; the shade is on the transparent platform to emit light; the scanning module is set on the slide rail in sliding mode to receive lkight emitted from the shade and transmitting the file and to produce corresponding detection signal. The compensating method is that when the scanning module slides on the slide rail to scan file, the detection signal the scanning module produces is amplified to attenuated based on the relative position of the scanning module to the slide rail. |