A laser light-source apparatus that comprises: a seed light source configured to output pulse light based on gain switching; a fiber amplifier (20, 30) configured to amplify the pulse light output from the seed light source; a solid state amplifier configured to amplify the pulse light output from the fiber amplifier (20, 30); a nonlinear optical element (60, 70) configured to perform wavelength conversion on the pulse light output from the solid state amplifier and output the resultant pulse light; an optical switching element that is disposed between the fiber amplifier (20, 30) and the solid state amplifier, and is configured to to be switched between an output stopped state, in which output of pulse light from the nonlinear optical element (60, 70) is stopped, and an output permitted state, in which pulse light with large peak power is output from the nonlinear optical element (60, 70); and a control unit configured to control the optical switching element in such a manner that the propagation of the light is stopped in an output period of the pulse light from the seed light source, and permitted in a period other than the output period of the pulse light from the seed light source to achieve the output stopped state in which the output of the pulse light from the nonlinear optical element (60, 70) is stopped, and to prevent giant pulse from generating when the pulse light from the nonlinear optical element (60, 70) is permitted to emit by releasing energy in an active region in the solid state amplifier by propagating amplified spontaneous emission noise generated in the fiber amplifier (20, 30) to the solid state amplifier; wherein the control unit is configured to control the optical switching element in such a manner that the propagation of the light is permitted in the output period of the pulse light from the seed light source after the output stopped state, and stopped in the period other than the output period of the pulse light from the seed light source to achieve the output permitted state in which the output of the pulse light from the nonlinear optical element (60; 70) is permitted. a seed light source configured to output pulse light based on gain switching; a fiber amplifier (20, 30) configured to amplify the pulse light output from the seed light source; a solid state amplifier configured to amplify the pulse light output from the fiber amplifier (20, 30); a nonlinear optical element (60, 70) configured to perform wavelength conversion on the pulse light output from the solid state amplifier and output the resultant pulse light; an optical switching element that is disposed between the fiber amplifier (20, 30) and the solid state amplifier, and is configured to to be switched between an output stopped state, in which output of pulse light from the nonlinear optical element (60, 70) is stopped, and an output permitted state, in which pulse light with large peak power is output from the nonlinear optical element (60, 70); and a control unit configured to control the optical switching element in such a manner that the propagation of the light is stopped in an output period of the pulse light from the seed light source, and permitted in a period other than the output period of the pulse light from the seed light source to achieve the output stopped state in which the output of the pulse light from the nonlinear optical element (60, 70) is stopped, and to prevent giant pulse from generating when the pulse light from the nonlinear optical element (60, 70) is permitted to emit by releasing energy in an active region in the solid state amplifier by propagating amplified spontaneous emission noise generated in the fiber amplifier (20, 30) to the solid state amplifier; wherein the control unit is configured to control the optical switching element in such a manner that the propagation of the light is permitted in the output period of the pulse light from the seed light source after the output stopped state, and stopped in the period other than the output period of the pulse light from the seed light source to achieve the output permitted state in which the output of the pulse light from the nonlinear optical element (60; 70) is permitted.