A headlamp unit (30) is mounted between opposite sides of a radiator core support panel (10) in a widthwise direction of a vehicle and a front portion of a front fender. One of a front mounting position of a front portion of the headlamp unit (30) and a rear mounting position of a rear portion of the headlamp unit (30) is provided with a fastening structure (50). The other one of the front mounting position and the rear mounting position is provided with an inserting structure (40) capable of adjusting an inserting amount. The headlamp unit (30) is allowed to slide and move by the fastening structure and/or the inserting structure, thereby making it possible to adjust a mounting position.