A laser scanning unit includes a scanning lens, a control portion, and a storage portion. The control portion controls a light amount of a light beam emitted from a light source. The storage portion stores therein aberration characteristics representing a relationship between image heights of the scanning lens and a wavefront aberration amount, which have been obtained in advance. The control portion, when the scanning is performed, controls the light amount of the light beam in accordance with the aberration characteristics, such that the light amount is set to a predetermined first light amount, at a point of a first image height where the wavefront aberration amount has a first value, and the light amount is set to a second light amount larger than the first light amount, at a point of a second image height where the wavefront aberration amount has a second value larger than the first value.