An imaging lens includes a first lens having positive refractive power; a second lens having negative refractive power; a third lens having negative refractive power; a fourth lens having positive refractive power; and a fifth lens having negative refractive power, arranged in this order from an object side to an image plane side. The first lens has an Abbe's number νd1, the second lens has an Abbe's number νd2, and the fourth lens and the fifth lens have a composite focal length f45 so that the following conditional expressions are satisfied: 45