This invention provides an image processing apparatus that corrects an image blur by using a plurality of images acquired by image capturing means. The apparatus comprises: blur detection means that detects a blur amount between the plurality of images; image composition means that performs the composition of the plurality of images using the detected blur amount; acquisition means that acquires, based on a difference value between the plurality of images and a threshold value thereof, region data for separating the image into regions by changing the threshold value; and display means that selectably displays the region data for each threshold value.