therefrom a grooved ball bearing 21 is secured to the end of the lower stem 3 b an actuator 31 for tilting movement is mounted on the back of the lamp body 1 via an opening 1 a confronting the grooved ball bearing 21 the spherical end 33 having a substantially spherical shape of an actuator rod 32 extends from the actuator 31 to the lamp body 1 so as to be fitted into the grooved ball bearing although detailed description and drawings are omitted the actuator 31 houses a motor and a worm wheel mechanism to be driven thereby such that the revolution drive from the motor extends and contracts reciprocate the actuator rod along its length the actuator 31 is controlled by a control circuit which is not shown in this embodiment it is constructed to function such that the optical axis is maintained at a predetermined angle based on an output signal from a level sensor for detecting the horizontal position of the vehicle body fig4 is an exploded perspective view of the lower stem 3 b and the grooved ball bearing 21 the lower stem 3 b includes a cylindrical boss 41 having a circular cross section and a cross shaped boss 42 having a cross shaped cross section both extending horizontally toward the back of the reflector 3 these two bosses are connected to each other via connector plates 43 44 extending between those bosses and between the cylindrical boss 41 and the reflector 3 respectively for the purpose of improving mechanical strength of the bosses 41 and 42 the cylindrical boss 41 has a threaded.