Abstract: A headlight device of the type including a lamp body formed of a synthetic resin material, a lens covering the front surface of the lamp body, an electric bulb provided in a lamp space defined between the lamp body and the lens, and a clearance lamp provided adjacent to one side edge of the lamp body. The lamp body has a parabolic surface reflective mirror portion opening in the forward direction, and an auxiliary reflective mirror portion extending from the left or right side edge portion of the parabolic surface reflective mirror portion of the side of the clearance lamp. The auxiliary reflective mirror portion is generally inclined in the direction toward the distal edge of the lens, and has a concave inner surface. The lens has a front surface portion, and at least one side wall portion extending in the rear direction from the side edge of the front surface portion adjacent to the clearance lamp.