This relatively inexpensive, compact laser light source device improves energy utilization efficiency when amplifying pulse light with a solid state amplifier and removes heat-generating loss of the amplifier, and comprises: a seed light source (10); a fiber amplifier that amplifies the pulse light output from the seed light source using gain switching; a solid-state amplifier that further amplifies that output; a non-linear optical element that performs wavelength conversion on the pulse light outputted from the solid-state amplifier; a light-switching element (40) which reduces ASE noise and which is positioned between the fiber amplifier (30) and the solid-state amplifier (50); and a control unit (100). The control unit controls the light-switching element so as to allow the propagation of light during the output of pulse light from the seed light source and hinder the propagation of light while pulse light is not being output, and cyclically or intermittently controls the excitation light source of the fiber amplifier and/or the solid-state amplifier in such a manner that the fiber amplifier and/or the solid-state amplifier inverts the pulse light output from the seed light source before input.