An optical scanning device includes an oscillating mirror part, a torsion bar part, a piezoelectric element (driving part), a housing, and an optical element part. The oscillating mirror part includes a reflective surface capable of reflecting light from a first light source and a mass adjustment part formed on an opposite surface of the oscillating mirror part to the reflective surface and configured to be capable of reducing a mass thereof by exposure to laser light. The torsion bar part supports the oscillating mirror part. The piezoelectric element is configured to torsionally oscillate the oscillating mirror part about the torsion bar part. The housing accommodates the oscillating mirror part, the torsion bar part, and the piezoelectric element. The optical element part is configured to reflect or transmit the laser light from a second light source disposed outside of the housing to expose the mass adjustment part to the laser light.