Provided is a variable wavelength laser device that achieves phase control of high precision while restraining thermal interference and stably outputs emission light of desired wavelength.The variable wavelength laser device of the present invention includes: an optical amplification means including a low-reflective surface that reflects light of wavelengths other than a predetermined wavelength and emits light of the predetermined wavelength; a wavelength control means for controlling wavelength of light being transmitted through the optical waveguide; a phase control means for controlling phase of light being transmitted through the optical waveguide using heat emitted by a heating means; a reflection means for totally reflecting the inputted light; and a heat dissipation means for restraining transfer of heat emitted by the heating means to regions other than a region in which the phase control means is disposed.