A head-up display device includes a display unit for displaying information, a reflector rotatably supported by frame members fixed to a vehicle, and an adjuster for adjusting a rotational position of the reflector by a gearing system. The information displayed on the display unit is reflected by the reflector to a projection area on a vehicle windshield. The adjuster so adjusts the rotational position to allow a vehicle driver to see both a front view through the windshield and a superimposed reflected image of the information. The head-up display device further includes a regulator to allow the reflector to rotate in a rotational direction within a range where the reflector is adjustable by the adjuster, and to prevent the reflector from shifting in a direction other than the rotational direction.