An optical scanning device that performs optical scanning across an object to be scanned with a light deflected, comprises: a deflection unit that causes a deflection mirror driven by a driving source to deflect the travel direction of light emitted from a light source and generates the light deflected; a resonator that includes a resonance space for reducing sound emitted from the deflection unit and a resonance passage communicating with the resonance space to direct sound from outside to inside the resonance space; a housing that accommodates the deflection unit and the resonator, and a partition wall that partitions a deflection unit accommodating space acting as a space for accommodating the deflection unit in the housing and a resonator accommodating space acting as a space for accommodating the resonator in the housing.