PURPOSE: To constitute the device so that a result of retrieval becomes that which is intended by a user by generating an inverted file by executing weighting corresponding to an appearance position in a document of an extracted keyword by a keyboard extracting part.

CONSTITUTION: The device is provided with a document format understanding part 8 for decoding a format of a document registered in a file 1, and an inverted file 2 is generated by executing weighting corresponding to an appearance position in a document for showing the significance in a document of an extracted keyboard by a keyword extracting part 3. Accordingly, the inverted file 2 containing the information regarding to what extent this keyword is significant in the document containing its keyword is generated and can be offered to the retrieval, and the retrieval for obtaining a result by which the document in which the keyword in a retrieval condition has significant semantics can take priority by super-ordinate ranking, etc., can be executed. In such a way, a result of retrieval intended by a user is obtained easily.