An image reading apparatus includes a plurality of light sources for illuminating an original, a photoelectric conversion device for converting light from the original illuminated by each of the plurality of illuminating means, and a discriminating circuit for discriminating whether or not any image exists on the original, based on image signals output from the photoelectric conversion device at least when the original is illuminated with light from one of the light sources, which possesses spectral characteristics including green. A control circuit controls the apparatus so that, when the discriminating circuit has determined that no image exists on the original, the manner of reading of the image with the light sources other than the light source employed in the discrimination performed by the discriminating circuit is changed from the manner of reading of the image with the light source employed in the discrimination.