An image encoder which attaches information unique to a frame to encoded moving-image data. An encoding unit compressively encodes moving-image data so as to produce pictures. First numbers respectively corresponding to the above pictures are obtained by counting the pictures. Frame information items unique to individual frames in the moving-image data are held in association with the first numbers, respectively. A header-information insertion unit receives ones of the above pictures, and inserts header information items into data of the ones of the pictures. Second numbers respectively corresponding to ones of the pictures are obtained by counting the ones of the pictures. The header-information insertion unit inserts one of the frame information items held in association with one of the first numbers identical to each of the second numbers, into a header information item corresponding to a predetermined portion of data of a picture which corresponds the second number.