A laser light source device has a semiconductor laser element, a heat transfer portion having thermal conductivity and connected to the semiconductor laser element, a cooler connected to the heat transfer portion on a side different from the semiconductor laser element, a control object temperature measurement section that measures a control object temperature as the temperature of the heat transfer portion or the cooler, an environmental temperature measurement section that measures an environmental temperature of the laser light source device, and a controller that controls the cooler. The controller is configured to control the cooler such that the control object temperature approaches a predetermined target temperature set according to the environmental temperature. The target temperature set when the environmental temperature is lower than a specific temperature is lower than the target temperature set when the environmental temperature is higher than the specific temperature.