An imaging lens includes a first lens group and a second lens group, arranged in this order from an object side to an image plane side. The first lens group includes a first lens, a second lens, and a third lens. The second lens group includes a fourth lens, a fifth lens having positive refractive power, a sixth lens having two aspheric surfaces, and a seventh lens having two aspheric surfaces. The imaging lens has a total of seven single lenses. The first to seventh lenses are arranged respectively with a space in between. The third lens is formed in a shape so that a surface on the object side is convex. The fourth lens is formed in a shape so that a surface on the object side is concave. The fifth lens is formed in a shape so that a surface on the image plane side is concave.