PROBLEM TO BE SOLVED: To provide a mechanism capable of efficiently performing temporal comparison on the fundus of an eye to be examined. A first image obtained by photographing an area of a predetermined size on a fundus of an eye to be examined and a second image obtained by photographing an area narrower than the area of the predetermined size. Different from the image acquisition unit 110 that acquires and are associated with each other based on the shooting time, and the first alignment that is the alignment between the first image and the second image that form the same set. A second alignment, which is the alignment of the first images included in the plurality of sets, is performed, and alignment information is generated by the alignment unit 141 and the alignment unit 141 that generates the positional information related to these alignments. A second image included in the first set and a second image included in the second set acquired after the first set are included in the first set based on the obtained position information. And a superimposing unit 142 that superimposes the first image included in the second set on the first image to generate a superimposed image. [Selection diagram] Figure 1【課題】被検眼の眼底における経時比較を効率良く行える仕組みを提供する。【解決手段】被検眼の眼底における所定の大きさの領域を撮影して得られた第１の画像と、前記所定の大きさの領域よりも狭い領域を撮影して得られた第２の画像とを、撮影時期に基づくセット毎に対応付けて取得する画像取得部１１０と、同一のセットを構成する第１の画像と第２の画像との位置合わせである第１の位置合わせと、異なる複数のセットに含まれる第１の画像の夫々の位置合わせである第２の位置合わせとを行って、これらの位置合わせに係る位置情報を生成する位置合わせ部１４１と、位置合わせ部１４１で生成された位置情報に基づいて、第１のセットに含まれる第２の画像と第１のセットよりも後に取得された第２のセットに含まれる第２の画像とを、第１のセットに含まれる第１の画像又は第２のセットに含まれる第１の画像に重畳させて、重畳画像を生成する重畳部１４２を備える。【選択図】図１
