An image-reading lens includes front-group and rear-group lens systems which are arranged on an object side and an image side, respectively. The front-group lens system includes equal to or less than 5 lenses which include at least one positive lens and at least one negative lens, and the rear-group lens system includes one negative lens. An angle of view of an entire system of the image-reading lens is equal to or more than 56°. The front-group and rear-group lens systems are structured such that with respect to a change in a distance between the front-group and rear-group lens systems, a change in a focal length of the entire system of the image-reading lens is small, and a change in an image plane is large, and by adjusting the distance between the front-group and rear-group lens systems, a required lens performance is obtained.