A wavelength tunable laser device includes a substrate including silicon, the substrate having a waveguide, a first semiconductor element bonded to the substrate, the first semiconductor element including an active layer of a group III-V compound semiconductor, and a second semiconductor element bonded to the substrate, the second semiconductor element facing to the first semiconductor element in a direction along which light emitted from the first semiconductor element propagates, the second semiconductor element including a grating formed of a group III-V compound semiconductor. The grating selects a wavelength of light.