A LIDAR unit includes: an LD driver, a laser diode, and a scanner corresponding to an emission unit; a photo detector, a current/voltage conversion circuit, a A/D converter and an valuable segmenter that correspond to a light receiving unit; a landmark position prediction unit and landmark map acquisition unit that acquire position information indicating the position of a landmark on a map; and a synchronization controller that generates a valuable pulse trigger signal and a segment extraction signal. Based on a predicted current vehicle position value and the position of the landmark on the map, the landmark position prediction unit determines a predicted angular range of the landmark. The synchronization controller generates the valuable pulse trigger signal and the segment extraction signal such that the scan density of the light pulse is higher in the predicted angular range than the scan density of the light pulse in the other range.