An image capturing apparatus including a plurality of photoelectric conversion portions for each of a plurality of microlenses, the image capturing apparatus comprising: a readout unit configured to be driven using a first driving method in which a signal is read out from part of the plurality of photoelectric conversion portions, and a second driving method in which a signal is read out from a greater number of the photoelectric conversion portions than in the first driving method; and a supply unit configured to, in a case where a signal is read out using the first driving method, supply an amperage that is smaller than that in a case where a signal is read out using the second driving method, to the readout unit.