An optical scanning device of opposed scanning type, includes: a plurality of light sources, being arranged substantially symmetrically about a rotating deflection unit; a group of pre-deflection optical elements including optical elements that make the light beams incident on the rotating deflection unit; and scanning optical systems which are distributed to right and left with the rotating deflection unit as an axis of symmetry, wherein optical elements of the respective scanning optical systems are arranged substantially symmetrically about the rotating deflection unit, wherein a plurality of rib structures are arranged on respective areas of an optical housing substrate, the areas extends from the respective light sources to a vicinity of the rotating deflection unit, and the plurality of rib structures are arranged asymmetrically in the right and left optical systems with the rotating deflection unit as the axis of symmetry.