1. An image processing apparatus comprising: an obtaining unit configured to obtain a plurality of image signals, which are captured from different viewpoints; a setting unit configured to set a focal plane in association with a reconstructed image to be generated from the plurality of image signals obtained by the obtaining unit; a generation unit configured to generate the reconstructed image focused at the focal plane set by the 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 concatenated image including, as frames, a plurality of reconstructed images generated by the generation unit in association with a plurality of different focal planes.