An optical scanning device includes: a light source; a first optical element that converts light emitted from the light source to parallel light; a deflection element that deflects the light in a fast scanning direction to scan a surface of an object to be scanned with the light at a constant speed; a second optical element that guides the light to the deflection element; and a third optical element that focuses the light deflected by the deflection element onto the surface of the object to be scanned, at least one surface among surfaces of the third optical element that intersect the light including a surface form which affects only one of fast scanning direction characteristics or slow scanning direction characteristics at an image plane.