An imaging apparatus includes an imaging element having pixel portions each having a plurality of photoelectric conversion units for each microlens. The imaging element can output a pixel signal depending on a pupil-divided light flux. An image processing LSI processes a video signal based on the pixel signal output from the imaging element. An imaging element control unit controls the operation of the imaging element. An exposure control unit performs exposure control for an optical lens unit and an imaging element. In the first mode, the operation for reading pixel signals from all of the plurality of photoelectric conversion units constituting the pixel portion of the imaging element is performed. In the second mode, the control for reading pixel signals from a part of the plurality of photoelectric conversion units and for stopping a circuit relating to the unused photoelectric conversion units by reading no pixel signal is performed.