To attain load balancing at the time of retrieval, and to stably ensure high response even in a situation that a communication capacity is limited by retrieving public information related with a preliminarily controlled area only in response to a retrieval request for designating an area including the controlled area.

A communicating part 6 is connected with some other information shared system to constitute a distributed information sharing system through a prescribed communication line. A destination of transfer selecting part 7 selects the other information shared system identification information (for example, address) of the designation of information transfer by referring to transfer information stored in a transfer information storing part 8. An area relation selecting part 9 refers to area attribute information stored in an area attribute storing part 10, and when public information and retrieval information is related with a controlled area, the area relation selecting part 9 transfers it to one of its own public information retrieving part 3, public information registering part 2, or public information presenting part 4 according to the content, and transfers it to the destination of transfer selecting part 7 as necessary (at the time of transferring it to the other information shared system).