A waveguide device , comprising: a first diffractive element configured to serve as a light guiding element of light-input and having a first grating (121a1) configured to diffract light (L1) of a wavelength to forward propagate as a first diffraction light (Ld1) with a first diffraction angle (θ1); a second diffractive element having a second grating (121b1) configured to diffract a rest part (L1') of the light (L1) of the wavelength that is not diffracted by the first diffractive element to forward propagate as a second diffraction light (Ld2) with a second diffraction angle (θ2) that is different from the first diffraction angle (θ1); a third diffractive element configured to serve as a light guiding element of light-output and having a third grating (121c1) and a fourth grating (121c2), the third grating (121c1) being configured to diffract the first diffraction light (Ld1) to propagate with the first diffraction angle (θ1), and the fourth grating (121c2) being configured to diffract the second diffraction light (Ld2) to propagate with the second diffraction angle (θ2); and a waveguide element configured to guide the first diffraction light (Ld1) propagated from the first diffractive element and the second diffraction light (Ld2) propagated from the second diffractive element to the third diffractive element ; wherein one of the first diffractive element and the second diffractive element is a transmissive diffractive element, and another of the first diffractive element and the second diffractive element is a reflective diffractive element; and wherein the second diffraction light (Ld2) will not enter the first diffractive element . a first diffractive element configured to serve as a light guiding element of light-input and having a first grating (121a1) configured to diffract light (L1) of a wavelength to forward propagate as a first diffraction light (Ld1) with a first diffraction angle (θ1); a second diffractive element having a second grating (121b1) configured to diffract a rest part (L1') of the light (L1) of the wavelength that is not diffracted by the first diffractive element to forward propagate as a second diffraction light (Ld2) with a second diffraction angle (θ2) that is different from the first diffraction angle (θ1); a third diffractive element configured to serve as a light guiding element of light-output and having a third grating (121c1) and a fourth grating (121c2), the third grating (121c1) being configured to diffract the first diffraction light (Ld1) to propagate with the first diffraction angle (θ1), and the fourth grating (121c2) being configured to diffract the second diffraction light (Ld2) to propagate with the second diffraction angle (θ2); and a waveguide element configured to guide the first diffraction light (Ld1) propagated from the first diffractive element and the second diffraction light (Ld2) propagated from the second diffractive element to the third diffractive element ; wherein one of the first diffractive element and the second diffractive element is a transmissive diffractive element, and another of the first diffractive element and the second diffractive element is a reflective diffractive element; and wherein the second diffraction light (Ld2) will not enter the first diffractive element . <EOS>