In a method of controlling an image reading apparatus, which has an illumination unit adapted to irradiate an object with first and second light rays in different frequency ranges, and a light-receiving unit adapted to receive light coming from the object, and to output a signal, and reads an image of the object by moving the illumination unit and light-receiving unit relative to the object, the light-receiving unit outputs a first signal in response to irradiation with the first light ray, and outputs a second signal in response to irradiation with the second light ray. Upon reading image information for one line by the image reading apparatus, the second light ray is controlled to be sequentially turned on at a plurality of timings to sandwich the ON timing of the first light ray, and image signals for one line corresponding to the first and second light rays are obtained by averaging or adding respective pieces of image information obtained at the plurality of timings for each of the first and second signals.