PURPOSE: To comprise an optical axis detection section without any contact and improve durability by using variable inductance for the directional detection of an optical axis, comparing the pulse width determined by the variable inductance value with the reference pulse width set arbitrarily, and adjusting the optical axis.

CONSTITUTION: When a variable resistor VR is operated in a reference pulse circuit 9 to adjust the optical axis of a headlight, the pulse width of a monostable multivibrator is varied. On the other hand, the inductance of variable inductance 6 automatically varies with the variation of the optical direction of the headlight and pulse width signals are output through an oscillator 7 and a waveform shaping circuit 8 according to the inductance. Then the output signals of each circuit 9 or 8 are compared in a comparison circuit 10. The relays Ry1 and Ry2 of a motor drive circuit 4 are controlled depending on the comparison result and then a motor 5 for adjusting the optical axis is rotated forward (or reversed) to remove a difference in the pulse width of each signal.