An optical scanning device includes a light source configured to emit a light beam; a rotary deflector configured to perform optical scanning by reflecting and deflecting the light beam emitted from the light source while rotating; an optical system forming member configured to form a path of the light beam; and a resonator having a resonance frequency corresponding to a sound generated by rotational drive of the rotary deflector. The rotary deflector is installed in a closed space. The resonator is installed so that the sound within the closed space is absorbed.