A semiconductor laser diode type of a buried-hetero structure (BH-LD) is disclosed. The LD provides a mesa, a first burying layer, and a second burying layer, where the burying layers are provided in respective sides of the mesa so as to expose a top of the mesa. The mesa includes a lower cladding layer, an active layer, and an upper cladding layer, where the cladding layers have conduction type opposite to each other and, combined with the burying layers, constitute a carrier confinement structure. The second burying layer has an even surface overlapping with an even surface of the first burying layer, and has a thickness in a portion of the even surface that is thinner than a thickness thereof in a portion except for the even surface.