An optical switch includes an input optical fiber, an output optical fiber, a grating which performs spectral separation of an optical signal to a plurality of optical signals having different wavelengths, a plurality of movable mirrors, each reflecting an optical light subjected to spectral separation, and directing the optical light appropriately to the input fiber, and each of the movable mirrors can be inclined, a mirror-angle detector which detects an angle of inclination of each of the movable mirrors, a table which associates a wavelength number which identifies the optical signals of the plurality of wavelengths, and an output-destination number which identifies the input optical fiber or the output optical fiber, with the angle of inclination of each movable mirror, and a control circuit which performs a feed-back control such that an angle of inclination AD which is output from the table and an output from the mirror-angle detector match.