1. An image capturing apparatus that captures an image of a target subject by image capturing means via focus control of an optical system, displays a captured image on a display means, and records a captured image on a recording medium by recording means, the image capturing apparatus comprising: image acquisition means for acquiring a plurality of captured images at least relating to the focus control among images captured by the image-capturing means; image comparison means for comparing focus states of focus positions of the plurality of captured images acquired by the image acquisition means; out-of-focus determination means for determining which captured images are not in focus, the captured images being included in the plurality of captured images compared by the image comparison means; and error display signal generating means for generating a signal for displaying an error region at the display means for the captured image determined to be out-of-focus by the out-of-focus determination means.