A head-up display device for a vehicle includes a housing, a temperature detector, and a light source control unit. The head-up display device projects, toward an external projection member, lights indicating display information for displaying an image produced by the reflected lights to a user positioned at a predetermined position. The housing houses the display portion and the light source disposed facing each other via heat transfer space. The temperature detector is disposed in a surrounding area of the display portion and the light source, and detects a temperature of the surrounding area. The light source control unit increases brightness of the emitted lights by increasing driving current of the light source when the detected temperature is lower than a reference low-temperature. The heat generated by the increased driving current is transferred to the display portion via the heat transfer space, and increases a temperature of the display portion.