A light scanning apparatus is provided in which a light source is controlled so that the total exposure energy density of when light beams are emitted to an image carrying member across light deflection scanning of a plurality of times becomes constant on the image carrying member, thereby high image quality, long lasting output images are obtained. Exposure energy density necessary when exposure is completed by light deflection scanning of one time is set to Ex1, the latent image electrical potential deepness of a latent image formed thereof is set to Vs1, total exposure energy density across light deflection scanning of a plurality of times is set to Ex_n, the latent image electrical potential deepness thereof is set to Vs_n, wherein Ex_n=Ex1−ΔEx and {(Vs_n/Vs1)^3−1.05}×Ex1