An imaging lens includes a first lens group; and a second lens group, arranged from an object side to an image plane side. The first lens group includes a first lens having negative refractive power and a second lens. The second lens group includes a third lens having positive refractive power and a fourth lens having negative refractive power. The fourth lens is formed in a shape so that a curvature radius of a surface thereof on the image plane side is positive. The first lens, the second lens and the third lens have specific Abbe's numbers, the first lens is arranged to be away from the second lens, the second lens is arranged to be away from the third lens, and the third lens is arranged to be away from the fourth lens by specific distances on an optical axis so that the specific conditional expressions are satisfied.