An imaging lens includes a first lens having negative refractive power; an aperture stop; a second lens; a third lens; a fourth lens; a fifth lens; and a sixth lens, arranged in this order from an object side to an image plane side. The fifth lens is formed in a shape so that a surface thereof on the image plane side is concave at a paraxial region thereof. The fifth lens is formed in the shape so that the surface thereof on the image plane side has an aspheric shape having an inflection point. The first lens has a specific Abbe's number ν1. The first lens is disposed away from the second lens by a specific distance. The fifth lens is disposed away from the sixth lens by a specific distance.