A diffraction grating light modulator composed of a plurality of diffraction grating light modulating elements formed on a substrate, each consisting of a lower electrode, belt-like fixed electrodes and movable electrodes supported above the lower electrode, and exposed connecting terminals (for electrical connection to external circuits) electrically connected to the movable electrodes, the fixed electrodes and the movable electrodes constituting a diffraction grating upon application of a voltage to the lower electrode, the diffraction grating light modulator having a protective electrode surrounding the connecting terminals, so that the diffraction grating light modulating element is certainly protected from damage by static electricity.