An imaging lens includes a first lens having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens; a fifth lens having negative refractive power; and a sixth lens having negative refractive power, arranged in this order from an object side to an image plane side. The sixth lens is formed in a shape so that a surface on the object side and a surface on the image plane side have negative curvature radii. The first lens has a specific focal length, the second lens has a specific focal length, the fourth lens is arranged to be away from the fifth lens by a specific distance on an optical axis, and the surface of the sixth lens on the image plane side has a specific curvature radius so that specific conditional expressions are satisfied.