A nitride-based semiconductor laser device capable of attaining stabilization of a laser beam and inhibiting a threshold current and an operating current from increase is provided. This nitride-based semiconductor laser device comprises a substrate consisting of either a nitride-based semiconductor doped with an impurity or a boride-based material, an n-type cladding layer formed on the substrate, an active layer consisting of a nitride-based semiconductor formed on the n-type cladding layer, a p-type cladding layer formed on the active layer and a light guide layer formed only between the active layer and the p-type cladding layer in the interspaces between the active layer and the n- and p-type cladding layers.