A head-up display comprising: a display device having a display surface for displaying an image; and a projection optical system for projecting an image displayed on the display surface onto a viewing area for an observer, wherein the projection optical system includes a first reflective element and a second reflective element in order along an optical path from the display surface to the viewing area, wherein a reflective surface of at least one of the first reflective element and the second reflective element has a concave shape, a light beam that is emitted from a center of the display surface and reaches a center of the viewing area is referred to as a reference light beam (Lc), an intersection of the reference light beam (Lc) with the reflective surface of the first reflective element is referred to as a reference intersection point , a plane including the reference light beam (Lc) incident on the first reflective element and the reference light beam (Lc) reflected by the first reflective element is referred to as a reference plane, an intersection line of the reflective surface of the first reflective element with the reference plane is referred to as a reference intersection line (Bc), a tangent plane of the reflective surface of the first reflective element at the reference intersection point is referred to as a reference tangent plane , respective heights from two points, a vertically upper point and a vertically lower point , which are equidistant from the reference intersection point on the reference tangent plane , to the reflective surface of the first reflective element are referred to as a sag, and when perpendiculars extending from the two points, the vertically upper point and the vertically lower point , and normal to the reference tangent plane intersect with the reference intersection line (Bc), a sag at the vertically upper point is greater than a sag at the vertically lower point . a display device having a display surface for displaying an image; and a projection optical system for projecting an image displayed on the display surface onto a viewing area for an observer, wherein the projection optical system includes a first reflective element and a second reflective element in order along an optical path from the display surface to the viewing area, wherein a reflective surface of at least one of the first reflective element and the second reflective element has a concave shape, a light beam that is emitted from a center of the display surface and reaches a center of the viewing area is referred to as a reference light beam (Lc), an intersection of the reference light beam (Lc) with the reflective surface of the first reflective element is referred to as a reference intersection point , a plane including the reference light beam (Lc) incident on the first reflective element and the reference light beam (Lc) reflected by the first reflective element is referred to as a reference plane, an intersection line of the reflective surface of the first reflective element with the reference plane is referred to as a reference intersection line (Bc), a tangent plane of the reflective surface of the first reflective element at the reference intersection point is referred to as a reference tangent plane , respective heights from two points, a vertically upper point and a vertically lower point , which are equidistant from the reference intersection point on the reference tangent plane , to the reflective surface of the first reflective element are referred to as a sag, and when perpendiculars extending from the two points, the vertically upper point and the vertically lower point , and normal to the reference tangent plane intersect with the reference intersection line (Bc), a sag at the vertically upper point is greater than a sag at the vertically lower point . <EOS>