A second harmonic wave-generation device for generating a second harmonic wave composed of an extraordinary ray from a fundamental wave composed of an ordinary ray, including a solid crystal of lithium potassium niobate-lithium potassium tantalate solid solution crystal or a single crystal made of lithium potassium niobate, wherein a mode field diameter of the fundamental wave inside the second harmonic wave-generation device is greater than that of the second harmonic wave.