A first image nonalignment amount, between a first type image and a second type image captured when the focusing lens is located at an in-focus position, of any subject, that is positioned a predetermined distance from the image capturing apparatus, is obtained. A second image nonalignment amount, between the first type image and the second type image obtained when the focusing lens is located at a predetermined reference position, of the subject is obtained. Then an image shift amount, for at least one of the first type image and the second type image captured when the focusing lens is located at the in-focus position, is determined, so that the difference between the first image nonalignment amount and the second image nonalignment amount falls within a predetermined range.