An image processing apparatus for processing imaging data, which is capable of generating a plurality of recomposed images respectively in focus at different subject distances, the image processing apparatus including an acquisition unit configured to acquire time-series imaging data capable of generating the recomposed image; a focal plane determination unit configured to determine a position of a focal plane in processing for generating the recomposed image; and a generation unit configured to generate recomposed-image data at the position of the focal plane determined by the focal plane determination unit, wherein the focal plane determination unit determines the position of the focal plane in the processing for generating the recomposed image based on the positions of the focal plane respectively corresponding to the time-series imaging data on which the processing for generating the recomposed image is to be performed.