Imaging lens

An imaging lens comprising:

• a first lens having positive refractive power;
• a second lens having negative refractive power;
• a third lens having positive refractive power;
• a fourth lens having negative refractive power;
• and
• a fifth lens having object-side and image plane-side surfaces thereof being aspheric, arranged in this order from an object side to an image plane side,
• wherein said first lens has a shape so that a curvature radius of a surface thereof on the object side is positive,
• said fifth lens has a shape so that a curvature radius of the surface thereof on the object side and a curvature radius of the surface thereof on the image plane side are positive, and
• said second lens, said third lens, and said fourth lens are arranged so that the following conditional expression is satisfied:
• 0.3<dA/dB<2.0
• where dA is a distance on an optical axis from a surface of the second lens on the image plane side to a surface of the third lens on the object side, and dB is a distance on the optical axis from a surface of the third lens on the image plane side to a surface of the fourth lens on the object side.