1. An image processing apparatus for generating a reconstructed image by performing a reconstruction process including a repetitive operation using a plurality of operation units, comprising: a memory storing a program; and one or more processors which, by executing the program, function as: an obtaining unit configured to obtain a plurality of measurement data of an object; a division unit configured to divide the plurality of measurement data into a plurality of subsets; a distribution unit configured to distribute the measurement data included in the plurality of subsets to the plurality of operation units in repetitive operation; a reconstruction processing unit configured to update results obtained by the plurality of operation units using the distributed measurement data, thereby performing the reconstruction process and generating partial reconstructed images on the plurality of operation units; and a combining unit configured to combine the partial reconstructed images to generate the reconstructed image, wherein a projection angle index corresponding to the projection angle is added to the measurement data, and the division unit designates the projection angle index, thereby dividing the plurality of measurement data into the plurality of subsets.