An optical scanning device including a light beam emission unit configured to emit a light beam, a main scanning line deflection unit configured to deflect the light beam in a main scanning direction to emit a scanning beam, a scanning lens configured to focus the scanning beam in the main scanning direction and a sub-scanning direction, a reflective optical element configured to deflect the scanning beam, a tilt adjustment unit configured to change a position of the reflective optical element to adjust a tilt of a scanning line of the scanning beam irradiating a target to be irradiated, and a curve adjustment unit configured to bend the reflective optical element to adjust a curve in the scanning line of the scanning beam irradiating the target to be irradiated.