a multiple beam scanning apparatus in which a plurality of light beams are repeatedly scanned at the same time , including a light source unit defining an optical axis and including plural laser diodes , collimator lenses for respectively converting light beams emitted by the laser diodes to respective parallel light fluxes , and a beam composing unit for superposing the light beams and emitting the superposed light beams therefrom . the light source unit is rotatively adjustable around the optical axis and is constructed such that respective light fluxes emitted from the beam composing unit are emitted with predetermined respective different angles at least in a main scanning direction .