PURPOSE: To switch over the headlamps properly according to running environment by switching over the direction of the headlamps of a vehicle based on the detection result of the quantity of light from an vehicle on the opposite lane, and varying a reference value for switching over from high beam to low beam according to the degree of the quantity of light injected from the vehicle on the opposite lane.

CONSTITUTION: A detector means, detecting the quantity of light emitted from a forward running vehicle or an vehicle on the opposite lane, is provided. It consists of No.1 and No.2 light-receiving sensors 1a and 1b each receiving a light of different wave-length range to make it possible to detect distinctly the headlamp light from the vehicle on the opposite lane or the tail lamp light from the forward running vehicle. The output signals from these light-receiving sensors 1a and 1b are input into a microprocessor 6 and a motor 3a as a drive means is driven and controlled to switch over the headlamps of the vehicle 2a and 2b to high beam or low beam. Also, the microprocessor 6 varies a reference value for switching over from high beam to low beam, according to the degree of the quantity of light injected from the vehicle on the opposite lane.