An imaging lens includes an aperture stop, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, and a sixth lens element arranged in order along an optical axis. The imaging lens satisfies ALT/T5≦6.90, where T5 is a thickness of the fifth lens element, and ALT is a summation of thicknesses of the six lens elements. Through designs of surfaces of the lens elements and relevant lens parameters, a short system length of the imaging lens may be achieved while maintaining good optical performance.