HEAD-UP DISPLAY DEVICE AND MOUNTING STRUCTURE FOR HEAD-UP DISPLAY DEVICE

A head-up display device includes a casing provided inside an instrument panel and provided with a concave mirror configured to project image information emitted from a light source onto a front windshield glass. In the head-up display device, a retraction portion is provided on a lower side of the concave mirror in a vehicle up-down direction and configured to allow the concave mirror to move downward in the vehicle up-down direction when an impact load is input to the concave mirror from an upper side in the vehicle up-down direction.