1. An image compositing apparatus comprising: a motion vector calculation unit configured to calculate a global motion vector reflecting an inter image global motion of a base image and a reference image and calculate a local motion vector reflecting an inter-image local motion between the base image and the reference image for one of a pixel and a unit region consisting of pixels; a moving region information calculation unit configured to calculate moving region information from the global motion vector and the local motion vector; an image correction unit configured to generate a corrected reference image obtained by correcting the reference image based on the global motion vector and a corrected reference image obtained by correcting the reference image based on the local motion vector; and a composition unit configured to composite the base image with the corrected reference image corrected based on the global motion vector and the corrected reference image corrected based on the local motion vector with composition ratios determined based on the moving region information, wherein the composition ratio of the corrected reference image corrected based on the global motion vector is higher than the composition ratio of the corrected reference image corrected based on the local motion vector in a region having the moving region information indicative of a moving region.