An imaging apparatus acquires pixel signals for each predetermined-size partial region of an imaging plane and for detecting a region among the regions of the imaging plane in which a subject image has changed, the number of acquired pixel signals being less than the number of pixels included in the partial region, and controls to perform image capturing in response to detection of the region in which the subject image has changed, and to output a captured image based the pixel signals. The imaging apparatus acquires pixel signals from each partial region of the imaging plane by, when pixel signals are to be acquired from a first partial region of the imaging plane, acquiring pixel signals from a second partial region that is adjacent to the first partial region and partially overlapped with the first partial region.