vapour discharge lamp 5 which is the light source is lit by closing headlight main switch 23 the light emitted from this light source is reflected by reflecting mirror 4 and is projected forward as a beam this beam passes through transparent cover 2 and illuminates the road surface ahead in this case when servo motor 15 which is the actuatoris operated headlight 3 rotates about center line of rotation p p and the axis of the beam can be rotated upward or downward between the lines 0 1 0 1 and 0 2 0 2 as shown in fig1 when the beam coincides with the line 0 1 0 1 the high beam is obtained and when it coincides with the line 0 2 0 2 the low beam is obtained however upward beam 0 1 0 1 and downward beam 0 2 0 2 must each be set with great accuracy the directions of these beams are determined by the amount of rotation u03b8 of headlight 3 and the vertical aiming position in the embodiment the amount of rotation u03b8 of headlight 3 and the vertical aiming position can be adjusted by servo motor 15 which acts as the actuator as shown in fig3 when the resistance of vertical aiming adjuster.