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 having positive refractive power, a second lens having positive refractive power and at least one aspheric surface, and a third lens having two aspheric surfaces, arranged with a space in between. The second lens group includes a fourth lens having two aspheric surfaces, a fifth lens having negative refractive power and two aspheric surfaces, and a sixth lens having two aspheric surfaces, arranged with a space in between. The third lens is arranged away from the fourth lens by a specific distance, and the fifth lens and the sixth lens have a specific composite focal length, so that specific conditional expressions are satisfied.