1. An image-processing apparatus comprising: a subject-detection unit configured to detect at least one subject image from inputted image data; an importance-determination unit configured to determine an importance of the at least one detected subject image; and a priority-determination unit configured to determine and output a priority of the at least one detected subject image based on the determined importance, wherein the importance-determination unit is further configured to determine the importance based on an importance previously determined by the importance-determination unit.