The present invention is intended to reduce variations in oscillation wavenumber of a semiconductor laser element due to the influence of circumferential temperatures. The invention includes a semiconductor laser semiconductor laser element, a temperature control part to control a temperature of the semiconductor laser element, a temperature sensor to detect a temperature of the temperature control part, and a temperature control device to control a supply signal to the temperature control part so that a detected temperature obtained from the temperature sensor reaches a predetermined target temperature. The temperature control device changes a target temperature for the temperature control part depending on a supply signal to the temperature control part.