A spectrometer includes: a dispersive element configured to split light; a detector comprising a plurality of pixels configured to receive the split light; an optical mask disposed in an optical path of the light between the dispersive element and the detector and comprising a plurality of light transmitting portions and a plurality of light blocking portions which are arranged alternately; and a driver configured to control a position of the optical mask or a position of the detector, and change a light incident area of each of the plurality of pixels to receive the light incident on the plurality of light transmitting portions of the optical mask.