A printer controller as an image processing apparatus having a plurality of processing units executes grouping a plurality of objects into one group for overlapping objects one of which overlaps with another object among the overlapping objects, and another group for independent object which does not overlap with another object. The printer controller calculates the drawing area for each of the groups obtained in the grouping process, and distributes the groups into the number of parallel processes to be executed by the plurality of processing units based on the calculated drawing area of each group.