A semiconductor laser device emitting a laser beam having stable emitting wavelength and a multimode spectrum is provided. The semiconductor laser device is a Fabry-Perot type semiconductor laser device having a layer structure including an active layer of a quantum well structure, and emitting a laser beam having wavelength stabilized by an action of return light and having a multimode spectrum, wherein each well layer satisfies relation: Γ/d≦1.3×10−3 nm−1 where Γ and d(nm) are an optical confinement factor and a thickness of a well layer, respectively.