1. An apparatus for determining the material of a printing media, the apparatus comprising: a light source for generating light to expose the printing media; an image sensor for detecting reflected light from the printing media to generate at least one image corresponding to the printing media; an image-analyzing unit, electrically connected to the image sensor, for analyzing the image to generate a material parameter and then determining the material of the printing media according to the material parameter; and a gradient index (GRIN) lens for gathering the reflected light from the printing media to focus on the contact image sensor; wherein the image sensor is a contact image sensor (CIS).