Optical scanning apparatus and image forming apparatus including same

An optical scanning apparatus, comprising:

• a housing body including a peripheral wall and a partitioning portion of a plate shape configured to divide an inner side of the peripheral wall into a first portion and a second portion, the partitioning portion including a first hole configured to cause the first portion to communicate with the second portion to form an optical path;
• a light deflector, which is mounted in the first portion, having a rotatable polygon mirror configured to perform deflection scanning of scanning light beams emitted from a plurality of light sources, and a drive unit configured to drive the rotatable polygon mirror to rotate through a drive shaft;
• a first optical system, which is mounted at least in the first portion, configured to cause the scanning light beams reflected from the rotatable polygon mirror to return towards the first hole;
• and
• a reinforcement member, which is mounted on a surface that faces at least the second portion on the partitioning portion, configured to reinforce the housing body.