PURPOSE: To eliminate the useless code conversion by identifying whether a request side and an offer side are the same code system or not from a request origin identification name and an offerer identification name given to transmitting/receiving information, and eliminating the code conversion in the case of the same code system.

CONSTITUTION: A request processing part 10 transmits request information, and an information offer processing part 11 registers an identification name for showing the request processing part 10 for using the same code system as directory information 3 in identification name information, fetches information designated by the request information from the directory information 3 and retrieves the identification name information. In such a state, in the case there is the identification name which coincides with a request origin identification name given to this request information, an offerer identification name of its information offer processing part 11 is given to offer information and it becomes reply information. In the case there is no identification name which coincides therewith, the offer information is converted to information shown by a prescribed standard code system and it becomes reply information. In such a way, the request processing part 10 identifies whether a conversion processing of a code extending from the standard code system to the own code system is necessary or not by the offer identification name given to the reply information and a useless code conversion is eliminated.