An image capturing apparatus includes an image sensor having a focus detection pixel group including a plurality of focus detection pixels that receive light passing through a part of a pupil area of an imaging lens for forming an object image and an image forming pixel group including a plurality of image forming pixels that receive light passing through the whole of the pupil area of the imaging lens; and an image processing unit that generates an image signal corresponding to the position of each of the focus detection pixels by using at least either of a signal of the focus detection pixel at the position and signals of neighboring image forming pixels of the focus detection pixel at the position, depending on the size of an aperture of the focus detection pixels.