A light source device includes: a fiber laser including an excitation light source and configured to output pulsed light generated according to excitation light from the excitation light source; a fiber amplifier configured to receive the pulsed light output from the fiber laser, amplify the pulsed light, and output the amplified pulsed light, a wavelength shift fiber configured to receive the pulsed light output from the fiber amplifier, shift a wavelength of the pulsed light, and output the pulsed light; an output fiber configured to receive the pulsed light output from the wavelength shift fiber, and output the pulsed light to an outside; a light detection element configured to detect, in the output fiber, the pulsed light having passed through at least the wavelength shift fiber; and a control unit configured to control a drive current of the excitation light source.