An optical scanning apparatus comprising: a first light source configured to emit a beam (LY) modulated in accordance with image information; a first deflection unit configured to deflect the beam (LY) emitted from said first light source , said first deflection unit including a first rotatable polygonal mirror with a first motor configured to reflect the beam (LY) emitted from said first light source ; a first scanning lens through which the beam (LY) reflected by said first rotatable polygonal mirror transmits; characterized by a second light source configured to emit a beam (LC) modulated in accordance with image information; a second deflection unit configured to deflect the beam (LC) emitted from said second light source , said second deflection unit including a second rotatable polygonal mirror with a second motor configured to reflect the beam (LC) emitted from said second light source ; a second scanning lens through which the beam (LC) reflected by said second rotatable polygonal mirror transmits, and a housing accommodating said first deflection unit, said second deflection unit said first rotatable polygonal mirror , and said second rotatable polygonal mirror , said housing including only three fixed portions fixed to a fixing portion configured to fix said optical scanning unit ; wherein said first rotatable polygonal mirror and said second rotatable polygonal mirror are disposed such that a rotational axis of said first rotatable polygonal mirror and a rotational axis of said second rotatable polygonal mirror are in a triangular area defined by lines connecting the three fixed portions , as viewed in a rotation axial direction of said first rotatable polygonal mirror . a first light source configured to emit a beam (LY) modulated in accordance with image information; a first deflection unit configured to deflect the beam (LY) emitted from said first light source , said first deflection unit including a first rotatable polygonal mirror with a first motor configured to reflect the beam (LY) emitted from said first light source ; a first scanning lens through which the beam (LY) reflected by said first rotatable polygonal mirror transmits; characterized by a second light source configured to emit a beam (LC) modulated in accordance with image information; a second deflection unit configured to deflect the beam (LC) emitted from said second light source , said second deflection unit including a second rotatable polygonal mirror with a second motor configured to reflect the beam (LC) emitted from said second light source ; a second scanning lens through which the beam (LC) reflected by said second rotatable polygonal mirror transmits, and a housing accommodating said first deflection unit, said second deflection unit said first rotatable polygonal mirror , and said second rotatable polygonal mirror , said housing including only three fixed portions fixed to a fixing portion configured to fix said optical scanning unit ; wherein said first rotatable polygonal mirror and said second rotatable polygonal mirror are disposed such that a rotational axis of said first rotatable polygonal mirror and a rotational axis of said second rotatable polygonal mirror are in a triangular area defined by lines connecting the three fixed portions , as viewed in a rotation axial direction of said first rotatable polygonal mirror . <EOS>