Provided is a reference angle position setting means for setting an optical axis at a reference angle position (direction of going straight ahead: 0) by detecting the maximum deflection angles when swivel lamps 3R and 3L are pivoted in one direction and in the opposite direction and gaining the reference angle position based on both the maximum deflection angles detected. Projector lamps are pivoted in one direction toward the reference angle position so as to set an optical axis position through the steps of detecting a first maximum deflection angle by pivoting each projector 30 lamp in one direction until it is no longer able to pivot in one direction, detecting a second maximum deflection angle by pivoting a headlamp in the opposite direction until it is no longer able to pivot in the opposite direction and computing the reference angle position of the irradiation optical axis from the first and second maximum deflection angles. Thus it is possible to not only set off the deflection produced in the projector lamps and the like but also accurately set the optical axis at the reference angle position at the time of bringing the projector lamps into contact with stoppers on both sides.