An image capturing apparatus comprises an image sensor including a first semiconductor substrate on which a photodiode is arranged, a second semiconductor substrate on which a storage element is arranged, and a connection unit configured to electrically connect the photodiode and the storage element, a first transfer unit configured to transfer pixel signals of a first pixel group to the storage element, a first readout unit configured to read out the pixel signals of the first pixel group, a second transfer unit configured to transfer pixel signals of a second pixel group to the storage element, and a second readout unit configured to read out some of the pixel signals of the second pixel group, wherein an image of one frame is generated by composing the pixel signals of the second pixel group and the first pixel group.