The present invention relates to a laser light source capable of suppressing variation in propagation state of randomly-polarized laser light. In the laser light source, an isolator including a Faraday rotation crystal having a positive thermooptic constant, and a nonlinear optical crystal having a negative thermooptic constant are arranged in order along a traveling direction of laser light. The nonlinear optical crystal is arranged in a state off normal incidence of incident light so that a propagation axis of light propagating in the crystal is parallel to an optic axis of the crystal.