1. An image processing system comprising: a first identification unit configured to identify a static area from an input image captured at each of a plurality of time points; an image generation unit configured to generate a first image by using the static areas of respective input images captured in a first time span from a processing time point and generate a second image by using the static areas of respective input images captured in a second time span from the processing time point; and a second identification unit configured to compare the first image and the second image and identify an area having a difference.