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 having positive refractive power; a fifth lens having negative refractive power; and a sixth lens having negative refractive power. The first lens has an object-side with a positive curvature radius. The second lens has object-side and image plane-side surfaces with positive curvature radii. The third lens has an image plane-side surface with a negative curvature radius. The fourth lens has object-side and image plane-side surfaces with negative curvature radii. The fifth lens has object-side and image plane-side surfaces with negative curvature radii. The sixth lens has strong positive refractive power close to a periphery, and an aspheric image plane-side surface having an inflexion point. The first to sixth lenses have specific Abbe's numbers to satisfy specific conditions.
