A light scanning device scanning a plurality of scanned faces by a light beam, includes a light source unit emitting a plurality of light beams including a first light beam and a second light beam having different polarization directions to each other; a beam splitter splitting each of the first light beam and the second light beam emitted from the light source unit; an incident optical system allowing each of split first light beams to be incident with an a angular difference to each other, and allowing each of split second light beams to be incident with an angular difference to each other; a deflector respectively deflecting each of the split first light beams and each of the split second light beams entered from the incident optical system; and a scanning optical system, including a polarization splitting device for splitting a plurality of the light beams deflected by the deflector based on a difference in a polarization direction, individually focusing each of the plurality of the light beams split by the polarization splitting device on a corresponding scanned face.