A semiconductor laser device includes an n type diffraction grating layer of n-InGaAsP on an n-InP substrate, and having through-holes periodically disposed alongside of one another in a laser optical waveguide direction, an n-InP layer containing S as a dopant impurity in a concentration of at least 1.times.10.sup.19 cm.sup.-3. The through holes are buried in the n-InP layer, and an active layer is disposed on both the n-InP layer and the diffraction grating layer through an n-InP cladding layer.