According to an embodiment, there are achieved an apparatus for image reading and a setting method for the apparatus with which adjusting workability is enhanced, an adjusting time is shortened and focusing of a 4-line CCD sensor as an optical sensor is set to the averagely best state. This embodiment is equipped with an optical sensor having plural line sensors having different numbers of pixels, a condenser lens for projecting an optical image to the optical sensor, and an adjusting mechanism for setting the distance between the condenser lens and the optical sensor so that the resolution of the line sensor having the largest number of pixels is highest among the plural line sensors.