The invention provides a compact laser light source whose wavelength can be designed freely in a wavelength band in which the semiconductor laser has not been put to practical use by combining an efficient nonlinear optical crystal and high-power semiconductor lasers for optical communication. In one embodiment, the laser light source includes: a first laser for generating a laser beam of a wavelength lambda1; a second laser for generating a laser beam of a wavelength lambda2; and a nonlinear optical crystal that allows the laser beam of wavelength lambda1 and the laser beam of wavelength lambda2 as inputs and outputs a coherent beam having a wavelength lambda3 of a sum frequency that satisfies a relationship of 1/lambda1+1/lambda2=1/lambda3. The wavelength lambda3 of the sum frequency is 589.3+/-2 nm that is equivalent to the sodium D line.