An imaging apparatus comprises an image sensing unit in which a plurality of photoelectric conversion elements are arranged on an image sensing plane, and a control unit. The control unit has a first mode in which image signals are read out from a first photoelectric conversion element group arranged in a first region of the image sensing plane, and a second mode in which image signals are read out from a second photoelectric conversion element group arranged in a second region that is smaller than the first region of the image sensing plane In addition, the control unit performs control such that a readout period of a line arranged on the image sensing plane in the first mode is substantially equal to that of a line arranged on the image sensing plane in the second mode when switching between the two modes.