1. An image processing apparatus comprising: an obtaining unit configured to obtain an image signal, which is captured by an image capturing apparatus, and in which a respective pixel corresponds to a light flux of a different combination of a pupil region, through which the light flux has passed, in an imaging optical system of the image capturing apparatus, and an incident direction; a setting unit configured to set a focal plane in association with a reconstructed image generated from the image signal obtained by said obtaining unit; a generation unit configured to generate the reconstructed image focused at the focal plane set by said setting unit by adding pixel values of the image signal, wherein the pixel values correspond to respective pixels of the image to be reconstructed at the focal plane; and an output unit configured to generate and output a moving image by including, as frames, a plurality of reconstructed images generated by said generation unit in association with a plurality of different focal planes.