An encoding device 100 encodes a plurality of input text files to a plurality of encoded files by using a static dictionary unit 121 and a dynamic dictionary unit 122. The dynamic dictionary unit 122 is generated in accordance with word appearance frequencies in the plurality of text files. The encoding device 100 generates a coupled encoded file that includes the plurality of encoded files, information on the dynamic dictionary unit 122, and position information that indicates positions of the respective plurality of encoded files.