A diagnosis processing apparatus for processing images of a diagnosis target existing in a structure to assess the structure, comprising: a storage unit configured to store i) data of a development-view image of the structure at a first inspection date, the development-view image being an image combining a plurality of images of the structure captured by scanning the structure, ii) position information indicating one or more positions used for capturing the plurality of images during the scanning, and iii) data of a plurality of wide-angle images captured at the first inspection date generated by capturing images of a wide area of the structure including a diagnosis target existing in the structure during the scanning, wherein the wide-angle images are associated with the position information; an acquisition unit configured to acquire data of a narrow-angle image captured at a second inspection date generated by capturing an image of an area of the structure including the diagnosis target, and data of a plurality of wide-angle images captured at the second inspection date generated by capturing images of a wide area of the structure including the diagnosis target existing in the structure; a similar image search unit configured to search for an image similar to a specific wide-angle image captured at the second inspection date from the plurality of wide-angle images captured at the first inspection date; and a display control unit configured to display a partial area image of the development-view image captured at a scanning position indicated by position information associated with data of a specific wide-angle image captured at the first inspection date as a narrow-angle image captured at the first inspection date, wherein the specific wide-angle image captured at the first inspection date is determined to be similar to the specific wide-angle image captured at the second inspection date and used for the searching. a storage unit configured to store i) data of a development-view image of the structure at a first inspection date, the development-view image being an image combining a plurality of images of the structure captured by scanning the structure, ii) position information indicating one or more positions used for capturing the plurality of images during the scanning, and iii) data of a plurality of wide-angle images captured at the first inspection date generated by capturing images of a wide area of the structure including a diagnosis target existing in the structure during the scanning, wherein the wide-angle images are associated with the position information; an acquisition unit configured to acquire data of a narrow-angle image captured at a second inspection date generated by capturing an image of an area of the structure including the diagnosis target, and data of a plurality of wide-angle images captured at the second inspection date generated by capturing images of a wide area of the structure including the diagnosis target existing in the structure; a similar image search unit configured to search for an image similar to a specific wide-angle image captured at the second inspection date from the plurality of wide-angle images captured at the first inspection date; and a display control unit configured to display a partial area image of the development-view image captured at a scanning position indicated by position information associated with data of a specific wide-angle image captured at the first inspection date as a narrow-angle image captured at the first inspection date, wherein the specific wide-angle image captured at the first inspection date is determined to be similar to the specific wide-angle image captured at the second inspection date and used for the searching.