An image display device used in a head-up display, the image display device comprising: an illumination unit including a plurality of light sources; a light guide plate including a first region including an incident surface through which light from the illumination unit enters, the incident surface including a plurality of convex surfaces which is opposed to the respective plurality of light sources, and a second region including a part of an output surface disposed in a direction intersecting the incident surface and from which the light incident from the incident surface is output; a light beam controller that controls a traveling direction of the light output from the output surface; and a display unit that is disposed above the second region, and that transmits the light output from the light beam controller to display an image, wherein the light guide plate includes a counter surface opposed to the output surface, wherein a first lenticular lens array is provided on the part of the output surface that is included in the first region, characterized in that a second lenticular lens array is provided on the part of the output surface that is included in the second region, wherein the first lenticular lens array is arrayed in a first direction, and the second lenticular lens array is arrayed orthogonal to the first direction, at least a part of the counter surface is inclined with respect to the output surface so that a thickness of the light guide plate in a third direction orthogonal to both the first direction and the second direction is kept constant in the first region and the thickness in the second region becomes thinner with increasing distance from the incident surface along the second direction. an illumination unit including a plurality of light sources; a light guide plate including a first region including an incident surface through which light from the illumination unit enters, the incident surface including a plurality of convex surfaces which is opposed to the respective plurality of light sources, and a second region including a part of an output surface disposed in a direction intersecting the incident surface and from which the light incident from the incident surface is output; an incident surface through which light from the illumination unit enters, the incident surface including a plurality of convex surfaces which is opposed to the respective plurality of light sources, and a second region including a part of an output surface disposed in a direction intersecting the incident surface and from which the light incident from the incident surface is output; a light beam controller that controls a traveling direction of the light output from the output surface; and a display unit that is disposed above the second region, and that transmits the light output from the light beam controller to display an image, wherein the light guide plate includes a counter surface opposed to the output surface, wherein a first lenticular lens array is provided on the part of the output surface that is included in the first region, characterized in that a second lenticular lens array is provided on the part of the output surface that is included in the second region, wherein the first lenticular lens array is arrayed in a first direction, and the second lenticular lens array is arrayed orthogonal to the first direction, at least a part of the counter surface is inclined with respect to the output surface so that a thickness of the light guide plate in a third direction orthogonal to both the first direction and the second direction is kept constant in the first region and the thickness in the second region becomes thinner with increasing distance from the incident surface along the second direction.