The present invention relates to a light distribution direction switching apparatus and a method of assembling the vehicle headlamp, the light distribution direction switching device is a fixed bracket (3) provided in the light source 21 forward of the vehicle headlamp; According to the rotational position by the pivoting pivoting shield to crack a portion of the light distribution emitted from the light source 21 (5); By pivoting the said pivoting shield (5) during operation of the actuator such that all of the irradiated light distribution (7); And a damper (9) to relieve the impact caused by the pivoting shield (5); doedoe comprises a, in the circumferential direction on the rim portion so that the damper (9) is abutting with the rotating shield (5), after it has protruding damping sheet 41; And the damping sheet 41 than the first damping protrusion 43 protrudes to the center of the damping sheet 41 to be in contact with the rotating shield (5); and characterized in that comprising a, thus pivoting the shield through the damper as the only can significantly reduce the vibration and noise caused by the impact, can reduce the light movements of the light source, in particular, the contact area of ​​the damping sheet to be abutting the pivoting shield is reduced and so can further enhance the buffering effect , rotate the shield so the first perforated fixing bracket for an assembler to fix the mounting bracket and the next I'm on a fixed bracket assembly to the vehicle body, thereby meeting the shield through the mounting bracket can be installed in place.