An optical scanning apparatus comprising: a first light source configured to emit a beam modulated in accordance with image information; a first deflection unit configured to deflect the beam 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 emitted from said first light source; a first scanning lens through which the beam reflected by said first rotatable polygonal mirror transmits; characterized by a second light source configured to emit a beam modulated in accordance with image information; a second deflection unit configured to deflect the beam 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 emitted from said second light source; a second scanning lens through which the beam 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 (40a, 40b, 40c) 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 (40a, 40b, 40c), as viewed in a rotation axial direction of said first rotatable polygonal mirror. a first light source configured to emit a beam modulated in accordance with image information; a first deflection unit configured to deflect the beam 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 emitted from said first light source; a first scanning lens through which the beam reflected by said first rotatable polygonal mirror transmits; characterized by a second light source configured to emit a beam modulated in accordance with image information; a second deflection unit configured to deflect the beam 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 emitted from said second light source; a second scanning lens through which the beam 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 (40a, 40b, 40c) 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 (40a, 40b, 40c), as viewed in a rotation axial direction of said first rotatable polygonal mirror.