An imaging lens includes a first lens; a second lens; a third lens; a fourth lens; a fifth lens; a sixth lens; and a seventh lens, arranged in this order from an object side to an image plane side. The imaging lens has a total of seven lenses. The first to seventh lenses are arranged respectively with a space in between. The first lens is formed in a shape so that a surface on the object side is convex near an optical axis. The third lens is formed in a shape so that a surface on the object side is convex near an optical axis. The seventh lens is formed in a shape so that a surface on the image plane side has at least one inflexion point and is concave near an optical axis. The fourth lens and the fifth lens have specific Abbe's numbers.