The present invention relates to a compact tunable laser device that can change the oscillation laser wavelength. The laser device includes: a laser diode chip 100 that emits laser light; an optical feedback-partial reflective mirror 500 that feeds some of light emitted from the laser diode chip 100 back to the laser diode chip 100 by reflecting it; a collimating lens 300 that is disposed in a light path between the laser diode chip 100 and the optical feedback-partial reflective mirror 500 and collimates light emitted from the laser diode chip 100; a tunable-selective filter 300 of which the transmissive wavelength changes in accordance with temperature; and a 45°-reflective mirror 400 that changes laser light traveling horizontally to a package bottom into laser light traveling perpendicular to the package bottom, wherein the laser diode chip 100 or the tunable-selective filter 300 is disposed on a thermoelectric element 900 and has an oscillation wavelength changing in accordance with a change in temperature of the thermoelectric element 900.