in an image readout lens comprising four lens elements having positive , negative , negative , and positive refracting powers , respectively , the glass material for at least one of the second and third lenses is defined in terms of relative partial dispersion and abbe number , so as to yield an image readout lens which favorably corrects chromatic aberration and is suitable as a color - image readout lens . disposed successively from the object side are a first lens l 1 made of a positive meniscus lens which is convex toward the object , a second lens l 2 and a third lens l 3 each having a surface on an image side concave toward the image and a negative refracting power , and a fourth lens l 4 made of a biconvex lens , wherein a lens glass material of at least one of the second lens l 2 and third lens l 3 satisfies the following conditional expression : θ g · f + 0 . 0019υ d & lt ; 0 . 650 where θ g · f is the relative partial dispersion of the lens glass material , and υ d is the abbe number of the lens glass material .