PURPOSE: To retrieve a word at high speed through a word dictionary, even if an input character-string does not exist at the head, by providing a word retrieving means for retrieving an object character-string by a result obtained by a character chain extracting means and an index retrieving means.

CONSTITUTION: From an input character-string inputted to a character chain extracting means 7, first of all, at least one piece of continuous character-string, namely, a character chain is derived. Subsequently, by using the character chain obtained by the means 7, an index retrieving means 8 retrieves a character chain index 8, and derives a word pointer in a word dictionary 10. That is, an address, etc., for instructing a word having a character chain stored in the index 9 are derived. As a result, a word in the dictionary 10 instructed by the word point obtained by the means 8 is retrieved by a matching means 11, and a word corresponding to the input character-string is derived. In this regard, the word pointer is used for both the retrieval of the index and the retrieval of the word dictionary, therefore, even if the input character-string does not exist at the head, an object word in the word dictionary can be retrieved at high speed.