1. An image processing apparatus comprising: an obtaining unit configured to obtain image data captured by an image sensor from which a reconstruction image can be generated by performing refocus processing on the image data; an image processing unit configured to generate a first reconstruction image from the image data at a focal plane at which a subject is detected; and a display unit configured to display the first reconstruction image and a second reconstruction image generated from the image data at a focal plane together, wherein the first and second reconstruction images include the subject, and wherein the image processing unit determines a plurality of focal planes for which a plurality of the first reconstruction images is to be generated, based on focal position information for respective positions in a screen of the image data output from the image sensor.