A headlight device (1) having a projection function includes a light source device (2), a lighting optical system (3), an image display element (4), an image signal controller (6), and a projection optical system (5). The projection optical system (5) includes a coaxial lens system (11) having a refractive action, a free-form surface lens (12), and a free-form surface mirror (13) from the image display element (4) side. In this way, an image that can be readily visually recognized by a driver or a pedestrian may be projected onto a road.