To provide a technique for generating a synthesized image which can generate synthesized image data in which face images of persons which have constant relationship are arranged collectively.

Adjacent synthesis positions are combined, grouping of the synthesis positions which are established on a template is performed, and order of the groups is determined according to the number of synthesis positions belonging to each of the groups. Face images of the persons contained in the image data such a group photography are detected, metric between adjacent person faces is measured, and face images of nearer persons are combined and distributed to each group by the determined order. The distributed face images are stuck on a synthesis position of each of the groups, and synthesized image data is generated. As a result, synthesized image data in which face images of persons which have constant relationship are arranged collectively can be generated easily.