An optical modulator having a protective film on a reflective layer is disclosed. One aspect of the invention provides an optical modulator having a protective film on a reflective layer, including a substrate; an insulation layer positioned on the substrate; a ribbon layer which has its center portion spaced apart from the insulation layer by a predetermined distance; an upper reflective layer, positioned on the center portion of the ribbon layer, which reflects or diffracts incident light; an upper-reflective-layer protective film, positioned on the upper reflective layer, which protects the upper reflective layer; and a piezoelectric element, positioned on the ribbon layer, which moves the center portion of the ribbon layer vertically. Certain embodiments of the invention prevent the deterioration and oxidation of the reflective layer surface due to heat or humidity, to maximize the light diffraction property and reliability of the optical modulator.