To sufficiently compress even corresponding point information when an image is compressed and encoded with key frames and corresponding point information between them.

A matching processor 16 generates the corresponding point information MF by calculating image matching between adjacent key frames. A format conversion part 300 converts the corresponding point information MF into data in image format. A map image compression part 302 compresses the data irreversibly by an image compressing method. Thus, the corresponding point information is converted into the data in the image format and then high compression effect can be expected.