A head-up display system, comprising: a detection device configured to detect positions of eyes of a user; and a head-up display, the head-up display comprising a display panel configured to display an image, an optical element configured to define a propagation direction of image light emitted from the display panel, an optical system configured to propagate the image light having a propagation direction defined by the optical element, toward the eyes of the user, and project a virtual image of the image onto a virtual image plane (Sv) which is positioned at a distance of 3.5 m to 7.5 m from the eyes of the user, and a processor configured to cause the display panel to display the image, the image comprising a first image (Ipl) and a second image (Ipr) which have a parallax with each other, the optical element being configured to propagate the first image (Ipl) displayed on the display panel, toward a first eye of the user, and to propagate the second image (Ipr) displayed on the display panel, toward a second eye of the user, the processor being configured to control the display panel such that the first image (Ipl) and the second image (Ipr) are projected as a three-dimensional image (Is) in a field of view of the user, and a convergence angle at which the user views a point on the three-dimensional image (Is) is equal to or less than a maximum convergence angle and is equal to or greater than a minimum convergence angle, the maximum convergence angle being greater by 0.43 degrees than a convergence angle for viewing a point on the virtual image plane (Sv), and the minimum convergence angle being less by 0.43 degrees than the convergence angle for viewing a point on the virtual image plane (Sv), wherein for the convergence angle for viewing a point on the virtual image plane (Sv), the three-dimensional image (Is) is positioned at an optimal viewing distance (Vd) on the virtual image plane (Sv) such that the first image (Ipl) and the second image (Ipr) are displayed at the same position, the processor being configured to be able to change a region where the first image (Ipl) is displayed and a region where the second image (Ipr) is displayed on the display panel based on the positions of the eyes of the user. a detection device configured to detect positions of eyes of a user; and a head-up display, the head-up display comprising a display panel configured to display an image, an optical element configured to define a propagation direction of image light emitted from the display panel, an optical system configured to propagate the image light having a propagation direction defined by the optical element, toward the eyes of the user, and project a virtual image of the image onto a virtual image plane (Sv) which is positioned at a distance of 3.5 m to 7.5 m from the eyes of the user, and a processor configured to cause the display panel to display the image, the image comprising a first image (Ipl) and a second image (Ipr) which have a parallax with each other, a display panel configured to display an image, an optical element configured to define a propagation direction of image light emitted from the display panel, an optical system configured to propagate the image light having a propagation direction defined by the optical element, toward the eyes of the user, and project a virtual image of the image onto a virtual image plane (Sv) which is positioned at a distance of 3.5 m to 7.5 m from the eyes of the user, and a processor configured to cause the display panel to display the image, the image comprising a first image (Ipl) and a second image (Ipr) which have a parallax with each other, the optical element being configured to propagate the first image (Ipl) displayed on the display panel, toward a first eye of the user, and to propagate the second image (Ipr) displayed on the display panel, toward a second eye of the user, the processor being configured to control the display panel such that the first image (Ipl) and the second image (Ipr) are projected as a three-dimensional image (Is) in a field of view of the user, and a convergence angle at which the user views a point on the three-dimensional image (Is) is equal to or less than a maximum convergence angle and is equal to or greater than a minimum convergence angle, the maximum convergence angle being greater by 0.43 degrees than a convergence angle for viewing a point on the virtual image plane (Sv), and the minimum convergence angle being less by 0.43 degrees than the convergence angle for viewing a point on the virtual image plane (Sv), wherein for the convergence angle for viewing a point on the virtual image plane (Sv), the three-dimensional image (Is) is positioned at an optimal viewing distance (Vd) on the virtual image plane (Sv) such that the first image (Ipl) and the second image (Ipr) are displayed at the same position, the processor being configured to be able to change a region where the first image (Ipl) is displayed and a region where the second image (Ipr) is displayed on the display panel based on the positions of the eyes of the user.