An image processing apparatus which composes a plurality of images shot under different exposure conditions, comprises a detection unit which detects an exposure error according to a position on a screen using, out of the plurality of images shot under different exposure conditions, an image whose exposure amount is smaller than a predetermined value as a detection target image, a calculation unit which calculates correction information to correct the exposure error detected by the detection unit in accordance with the position on the screen, an adjustment unit which performs level adjustment according to the exposure amount of the detection target image in accordance with the correction information and position information on the screen, and an image composition unit which generates a composite image by composing the plurality of images including the image that has undergone the level adjustment.