A light source device for a fiber optic gyroscope configured to drive a fiber optic gyroscope having a fiber optic coil, the light source device comprising: a laser light source that emits a laser light of a predetermined frequency; a stabilizing part that stabilizes the predetermined frequency of the laser light emitted from the laser light source; and a bandwidth broadening part that makes the laser light stabilized by the stabilizing part into a light having a continuous broadband spectrum; wherein the bandwidth broadening part comprises an optical comb generation part and a white noise modulation part; wherein either: the laser light stabilized by the stabilizing part is inputted into the optical comb generation part, which emits a light having a plurality of spectra equally spaced at predetermined intervals with a predetermined frequency as a center, and the light emitted from the optical comb generation part is inputted into the white noise modulation part, which performs frequency modulation using white noise for making a continuous spectrum with a modulation width equal to or more than a predetermined interval of a plurality of spectra; or the laser light stabilized by the stabilizing part is inputted into the white noise modulation part, which performs frequency modulation using white noise for making a continuous spectrum with a predetermined modulation width, and the light emitted from the white noise modulation part is inputted into the optical comb generation part, which emits a light having a plurality of spectra equally spaced at predetermined intervals that are is equal to or less than a predetermined modulation width by using white noise, with a predetermined frequency as a center. a laser light source that emits a laser light of a predetermined frequency; a stabilizing part that stabilizes the predetermined frequency of the laser light emitted from the laser light source; and a bandwidth broadening part that makes the laser light stabilized by the stabilizing part into a light having a continuous broadband spectrum; wherein the bandwidth broadening part comprises an optical comb generation part and a white noise modulation part; wherein either: the laser light stabilized by the stabilizing part is inputted into the optical comb generation part, which emits a light having a plurality of spectra equally spaced at predetermined intervals with a predetermined frequency as a center, and the light emitted from the optical comb generation part is inputted into the white noise modulation part, which performs frequency modulation using white noise for making a continuous spectrum with a modulation width equal to or more than a predetermined interval of a plurality of spectra; or the laser light stabilized by the stabilizing part is inputted into the white noise modulation part, which performs frequency modulation using white noise for making a continuous spectrum with a predetermined modulation width, and the light emitted from the white noise modulation part is inputted into the optical comb generation part, which emits a light having a plurality of spectra equally spaced at predetermined intervals that are is equal to or less than a predetermined modulation width by using white noise, with a predetermined frequency as a center. the laser light stabilized by the stabilizing part is inputted into the optical comb generation part, which emits a light having a plurality of spectra equally spaced at predetermined intervals with a predetermined frequency as a center, and the light emitted from the optical comb generation part is inputted into the white noise modulation part, which performs frequency modulation using white noise for making a continuous spectrum with a modulation width equal to or more than a predetermined interval of a plurality of spectra; or the laser light stabilized by the stabilizing part is inputted into the white noise modulation part, which performs frequency modulation using white noise for making a continuous spectrum with a predetermined modulation width, and the light emitted from the white noise modulation part is inputted into the optical comb generation part, which emits a light having a plurality of spectra equally spaced at predetermined intervals that are is equal to or less than a predetermined modulation width by using white noise, with a predetermined frequency as a center.