A scanning apparatus includes a scanning module. The scanning module includes plural light emitting diodes, a porous reflective plate with plural openings, and a reflective element. When the scanning apparatus starts scanning a document, the light beams emitted by the light emitting diodes are directed to the porous reflective plate. A portion of light beams reflected by the porous reflective plate are defined as reflected light beams. The light beams penetrating through the openings are diffracted to be diffractive penetrated light beams. The reflected light beams reflected by the reflective element and the diffractive penetrated light beams are projected on the document, so that enhanced uniform illumination efficacy is achieved.