An image pickup apparatus includes an image pickup unit including a plurality of photoelectric conversion elements provided correspondingly to each of microlenses arranged two-dimensionally, reads out a first signal through addition from the photoelectric conversion elements corresponding to the microlense, reads out a second signal from one of the photoelectric conversion elements corresponding to the microlense, and sets one of a first and second read-out modes to read signals from the image pickup unit in accordance with a photographing condition, wherein the first and second read-out modes differ in read-out density of the second signal in a read-out area in accordance with one of a thinning-out rate and an addition rate of a area from which the second signal is read out being different as compared to a area from which the first signal is read out.