A spectrometer includes a light source to project a light beam to a target object, an optical element including a plurality of apertures through which the light beam reflected by the target object transmits, a diffraction element to form diffracted images from a plurality of light beams having transmitted through the optical element, and a light receiving element to receive the diffracted images formed by the diffraction element and including an optical shield to block a diffracted image other than a certain-order diffracted image.