A waveguide lens includes a substrate, a planar waveguide, a media grating, a modulating electrode, and two ground electrodes. The planar waveguide is formed on the substrate and is coupled to a laser light source which emits a laser beam into the planar waveguide. The media grating is formed on the planar waveguide and arranged along a direction that is substantially parallel with an optical axis of the laser beam. The modulating electrode is positioned on and covers the media grating. The ground electrodes are positioned on two sides of the planar waveguide and opposite to each other. The modulating electrode and the ground electrodes cooperatively change an effective refractive index of the planar waveguide to change an effective focal length of the diffractive waveguide lens, utilizing an electro-optical effect, when an electric field is applied thereto.