1. A translation memory adapted to sentence-based translation comprising: a first retrieval dictionary of a first language having a first dictionary TRIE structure and a first index TRIE structure; and a second retrieval dictionary of a second language having a second dictionary TRIE structure and a second index TRIE structure, the first and second dictionary TRIE structures respectively storing sub character strings on respective paths from roots to multiple nodes thereof, the first and second index TRIE structure respectively storing index information to specify the sub character strings stored in the first and second dictionary TRIE structures, the index information stored in the first retrieval dictionary including identification information that identifies the index information to specify the sub character strings in the second retrieval dictionary that are translations of those in the first retrieval dictionary.