A signature device including a storage unit configured to store moving image data, and a processor configured to extract original metadata from moving image data for the image data of each of a plurality of images forming the moving image data, the original metadata including location data of the image data and identification data of the moving image data, to encode the image data of each of the images into still image data in accordance with an image format, to write the still image data into a first area, to write the original metadata extracted by the extractor into a second area, the first area and the second area being included in a storage area of a still image data file in which the still image data is filed, and to generate summary data for the still image data file.