A semiconductor laser device includes: an active layer; upper waveguide layers and a lower waveguide layer sandwiching the active layer therebetween; upper and lower cladding layers sandwiching the active layer and the upper and lower waveguide layers therebetween; and a current-narrowing layer defining a current-injection region for injecting current to the active layer, wherein a diffraction grating having a periodical structure in a resonance cavity direction is buried in any one of the waveguide layers, the diffraction grating being present in at least a part of the current-injection region; and the waveguide layer in which the diffraction grating is buried and the cladding layer adjoining to that waveguide layer forms an interface which is substantially flat in the resonance cavity direction. With the constitution, a waveguide structure which has a diffraction grating offering a higher flexibility in design and manufacture in terms of the coupling efficiency is realized, thereby easily providing a dynamic single-mode semiconductor laser device with higher reproducibility, yield and reliability.