1. An image processing apparatus comprising: an obtaining unit configured to obtain a plurality of images that are photographed with different exposure values including a proper exposure value while changing a photographing target area continuously; a detection unit configured to detect an overlapped area where an object overlaps between adjacent images among the plurality of images obtained by said obtaining unit; a generation unit configured to generate a composite area in which overlapped areas detected by said detection unit are overlapped so as not to exceed a predetermined count; a computation unit configured to compute composition ratios of the plurality of images obtained by said obtaining unit based on the exposure values and signal values at the times when the plurality of images are photographed; and a composition unit configured to generate a wide-angle composite image by compositing images in the composite area generated by said generation unit with the composition ratios computed by said computation unit.