An optical scanning apparatus includes a housing that positions and holds a plurality of light sources emitting light beams, a deflection mirror that deflects the light beams to perform main scanning, and at least one of optical image forming elements closest to the deflection mirror to form images on respective image carriers. A plurality of reflectors guide the light beams exiting the housing to the respective image carriers. A pair of support members face each other to support the housing in a main scanning direction. A support mechanism supports the reflectors by bridging the reflectors between the support members and also couples the support members to each other. Relative positions of the reflectors are arranged in a cross-sectional plane perpendicular to a main scanning direction between the support members.