Disclosed is a method for driving a wavelength-swept light source that includes an optical resonator in which an optical gain medium for emitting light, a wavelength selection element for selecting a wavelength of light emitted from the optical resonator, and an optical intensity modulation element for modulating intensity of light within the optical resonator are arranged and that is configured to sweep the wavelength of the emitted light. The method includes driving the optical intensity modulation element and the wavelength selection element in synchronization with each other to keep an instantaneous spectral width of the emitted lights constant.
