A virtual image display device comprising: - an image display element; - a collimating optical system to form a pencil coming from each pixel of the image display element into parallel pencil groups traveling in different directions; and - an optical device comprising: an optical waveguide to guide parallel pencil groups from the image display element meeting a condition of internal total reflection inside the optical waveguide by internal total reflection of the parallel pencil groups; a first reflection volume hologram grating provided in a position opposite to a light incident port (13a1) at an optical surface (13a, 23a, 43b) of the optical waveguide and having recorded thereon a plurality of interference fringes having a predetermined slant angle and identical to each other to diffract and reflect the parallel pencil groups incident upon the optical waveguide from outside and traveling in different directions as they are so as to meet the condition of internal total reflection inside the optical waveguide; and a second reflection volume hologram grating provided in a position opposite to a light- outgoing port (13a2) at an optical surface of the optical waveguide and having recorded thereon a plurality of interference fringes having a predetermined slant angle and identical to each other to project the parallel pencil groups guided by internal total reflection inside the optical waveguide as they are from the optical waveguide by diffraction and reflection thereof so as to depart from the condition of internal total reflection inside the optical waveguide, wherein the first and second reflection volume hologram gratings (14, 15) are disposed with the plurality of interference fringes recorded thereon being symmetrical with each other with respect to a predetermined plane of symmetry wherein the first and second reflection volume hologram gratings have their interference fringes disposed on the optical surface (13a, 23a, 34b) of the optical waveguide to be symmetrical with respect to a plane perpendicular to the optical surface (13a, 23a, 43b), wherein a slant angle φ0 of the interference fringe when a parallel pencil is incident at an angle θr and diffracted and reflected at an angle θs is given by the following equation based on the Bragg condition: φ0 = (θs + θr)/2. and wherein the slant angle φ0 is not equal to zero. - an image display element; - a collimating optical system to form a pencil coming from each pixel of the image display element into parallel pencil groups traveling in different directions; and - an optical device comprising: an optical waveguide to guide parallel pencil groups from the image display element meeting a condition of internal total reflection inside the optical waveguide by internal total reflection of the parallel pencil groups; a first reflection volume hologram grating provided in a position opposite to a light incident port (13a1) at an optical surface (13a, 23a, 43b) of the optical waveguide and having recorded thereon a plurality of interference fringes having a predetermined slant angle and identical to each other to diffract and reflect the parallel pencil groups incident upon the optical waveguide from outside and traveling in different directions as they are so as to meet the condition of internal total reflection inside the optical waveguide; and a second reflection volume hologram grating provided in a position opposite to a light- outgoing port (13a2) at an optical surface of the optical waveguide and having recorded thereon a plurality of interference fringes having a predetermined slant angle and identical to each other to project the parallel pencil groups guided by internal total reflection inside the optical waveguide as they are from the optical waveguide by diffraction and reflection thereof so as to depart from the condition of internal total reflection inside the optical waveguide, an optical waveguide to guide parallel pencil groups from the image display element meeting a condition of internal total reflection inside the optical waveguide by internal total reflection of the parallel pencil groups; a first reflection volume hologram grating provided in a position opposite to a light incident port (13a1) at an optical surface (13a, 23a, 43b) of the optical waveguide and having recorded thereon a plurality of interference fringes having a predetermined slant angle and identical to each other to diffract and reflect the parallel pencil groups incident upon the optical waveguide from outside and traveling in different directions as they are so as to meet the condition of internal total reflection inside the optical waveguide; and a second reflection volume hologram grating provided in a position opposite to a light- outgoing port (13a2) at an optical surface of the optical waveguide and having recorded thereon a plurality of interference fringes having a predetermined slant angle and identical to each other to project the parallel pencil groups guided by internal total reflection inside the optical waveguide as they are from the optical waveguide by diffraction and reflection thereof so as to depart from the condition of internal total reflection inside the optical waveguide,