In an image reader, delay circuits are disposed on connection lines connecting an A/D converter with an image data generation circuit, whereby the output timings of the digital electric signals output from the A/D converter differ. Thus, the digital electric signals are not output at the same time from the adjacent output terminals of the A/D converter. Thus, the digital electric signals output from the A/D converter do not make a low to high or high to low transition at the same time and amplifying of EMI is decreased. Therefore, noise can be prevented from being contained in image data generated by the image data generation circuit and the quality of the image read through the image reader can be improved.