Provided is a light projection device, and includes: a light source having plural light emission portions arranged side by side in a predetermined direction; a projection lens; and an optical scanner having a mirror portion which scans light passed through the projection lens in a direction that the light emission portions are aligned, and a drive source swinging the mirror portion. The mirror portion scans a scanning light, which is irradiated from each light emission portion and scanned by the mirror portion, to form an intensity distribution having a central valley part and peaks located on both sides of the valley part. The optical scanner scans the light irradiated from the light emission portions in a manner that at least a peak of an intensity distribution of scanning light of other light emission portion is located in the valley part of the intensity distribution.