The present invention provides a light source apparatus capable of producing stable oscillation and performing high-speed wavelength sweeping over a desired wavelength range. A swept light source apparatus in which oscillation wavelength is continuously changeable is provided. The apparatus includes, inside a resonator, an optical amplification medium that amplifies light, a first device configured to disperse light emitted from the optical amplification medium and thus produce beams having different wavelengths, a second device functioning as a non-focusing optical element and configured to collimate the beams having different wavelengths resulting from the dispersion by the first device, and a selecting device configured to select a beam having a specific wavelength from among the beams collimated by the second device. The beam having the specific wavelength selected by the selecting device is fed back to the optical amplification medium.