A semiconductor laser device comprising an AlxGa1 xAs (x>/=0.3] quantum well active region having a thickness of 200 ANGSTROM or less, AlyGa1 yAs (y @x) carrier supplying layers sandwiching said quantum well active region therebetween, and an AlzGa1 zAs (z>y) cladding layer disposed on each of said carrier supplying layers, wherein an AlwGa1 wAs (w>z) barrier layer is disposed between each of said carrier supplying layers and each of said cladding layers.