An optical scanning device has an optical housing. A coupled Helmholtz resonator having a first resonance space and a second resonance space therein is disposed in the optical housing. A translucent partition wall, a first partition wall, and a second partition wall which extend from a bottom wall to a top wall of the optical housing are arranged in this order from an upstream side toward a downstream side on an optical path between a light source and a rotary polygonal mirror. The first and second resonance spaces are separated from each other by the three partition walls. One of the first and second resonance spaces resonates at a frequency of a rotational speed of a motor, and the other of the first and second resonance spaces resonates at a generated frequency of a wind noise generated by the rotary polygonal mirror.