A light projecting device includes a supporting unit, a first light source, a second light source, a light guiding unit and a lens. The first light source and the second light source are disposed on the supporting unit. The first light source includes a first lighting unit having a first light emitting surface. The second light source includes a second lighting unit having a second light emitting surface. The light emitting direction of the first light emitting surface is opposite to that of the second light emitting surface, and the first light emitting surface is substantially coplanar with the second light emitting surface. The light guiding unit is disposed in front of the supporting unit and the lens is disposed in front of the light guiding unit. Therefore, the light utilization efficiency of the light projecting device can be increased while satisfying requirements for miniaturization.