1. An image display apparatus which divides an image into a plurality of partial images, each having a region overlapping an adjacent partial image, and displays each of the plurality of partial images on an associated one of a plurality of displays to allow a viewer to view the partial images displayed on the plurality of displays as a single image, said image display apparatus comprising: a reception unit configured to receive an image signal corresponding to the image; a storage unit configured to store the image signal received by said reception unit in a buffer on a partial-image-by-partial-image basis; a correction unit configured to correct the image signal so that correction appropriate to an optical system of a display associated with each of the plurality of partial images is applied to the partial image; and a control unit configured to change the speed of correction processing performed by said correction unit for each partial image represented by an image signal stored in the buffer.