It is an object of the present invention to provide a multi wavelength laser device that can provide a plurality of lights after wavelength conversion which are superposed on the same axis with a simple structure, and that can ease restrictions imposed on the lights which are superposed. The multi wavelength laser device includes a laser light source 10 that emits a plurality of laser lights 20 whose fundamental wavelengths differ from one another, a dispersing element 30 that changes the traveling direction of each of the plurality of laser lights emitted from the laser light source 10 according to the wavelength and the incidence direction, and that emits the laser lights in a state in which the laser lights are superposed on the same axis, and a wavelength conversion element 40 that has a polarization inverted region and a polarization non-inverted region which are formed periodically, and that performs wavelength conversion on the plurality of fundamental wave laser lights emitted from the dispersing element 30 and placed in the state in which the laser lights are superposed on the same axis, and emits a plurality of laser lights 50 acquired through the wavelength conversion in a state in which the laser lights are superposed on the same axis.