In a plurality of pieces of single report structured data that is stored in a structured database in a diagnosis information database, character information constructing a radiological report describing detailed information of image data is added as metadata for search to the image data. For example, only by designating image data to be read as image (retrieval reference image) data as a reference of retrieval by a reading physician as the user during radiological operation, the character information already added to the retrieval reference image data is set as a keyword. By a keyword search using the metadata, data of a similar image and a related report of the retrieval reference image data are detected from the structured DB.