In a laser beam scanning apparatus, first and second laser beam emitters emit a laser beam polarized in a specific direction and a laser beam polarized in the direction orthogonal with this specific direction. A prism passes a laser beam emitted from the first laser beam emitter but reflects a laser beam emitted from the second laser beam emitter, and amalgamates two laser beams emitted from the first and second laser beam emitters in almost the same direction. A rotating polygonal mirror and a scanning lens simultaneously scan on a scanned plane two laser beams amalgamated by the prism. A 1/4 wavelength plate is inserted between the rotating polygonal mirror and the prism to change the laser beam from the prism from a linearly polarized state to a circularly polarized state. By the above arrangement, a difference of reflection factors between two laser beams incident to the rotating polygonal mirror can be eliminated so that two uniform laser beams can be scanned at the same time.