An image capturing apparatus comprises an image sensor; a readout unit that reads out an added signal and that independently reads out the signal of the first photoelectric conversion portion; a calculation unit that calculates a signal corresponding to a signal of the second photoelectric conversion portion by subtracting the signal of the first photoelectric conversion portion from the added signal; a correlation calculation unit that performs correlation calculation for the signal of the first photoelectric conversion portion and the signal corresponding to the signal of the second photoelectric conversion portion; and a subtraction unit that subtracts, from the result of the correlation calculation on an object image by the correlation calculation unit, a correction value for correcting noise caused by obtaining the signal corresponding to the signal of the second photoelectric conversion portion.