Provided is an external-resonance laser device for which a nonlinear optical crystal is arranged outside of the resonator, and which has high wavelength conversion efficiency. This laser device is characterized by having: a laser generation means (1) that generates high-intensity laser light
a nonlinear optical crystal (3) to which the high-intensity laser light generated by the laser generation means (1) is incident, and which generates second harmonic wave light
and a different-element flux-less growth nonlinear optical crystal (2) to which the second harmonic wave light generated by the aforementioned nonlinear optical crystal is incident, and which generates fourth harmonic wave light. In addition, the different-element flux-less growth nonlinear optical crystal is not damaged even when high-intensity laser light of 100 MW/cm2 or greater is incident.