An apparatus includes an imaging unit configured to perform imaging by using a plurality of image capture elements for accumulating electric charges, a storage unit configured to store an offset correction image, a correction image generation unit configured, when capturing a radiation image through radiant-ray irradiation, to combine the offset correction image with an image captured by using a part of the plurality of image capture elements through the imaging unit without radiant-ray irradiation to update the offset correction image, and a correction processing unit configured to correct the captured radiation image, based on the offset correction image.