If a beam state of headlight is manually switched over in a manual control mode, threshold values of vehicle speed, steering angle or the like, are learned for determining the switching over to the low-beam state or to the high-beam state based on the results detected by a speed sensor, illumination sensor, steering angle sensor and weather sensor, and are stored in a nonvolatile memory. In an automatic control mode, a CPU determines the switching over to the low-beam state or to the high-beam state based on the traveling condition detected by the illumination sensor by using the threshold values for determining the switching over learned in the manual control mode. The CPU automatically switches over the state of the beam of the headlight based upon the determination result.