A peer node according to the present invention relates to a peer node for constructing a peer-to-peer (P2P) network allowing P2P type communication. The peer node includes a unit dividing a share target file for information sharing through the P2P network into a plurality of divided files in a form where contents of each divided file makes no sense by itself; a unit distributing and arranging the plurality of divided files to and in a plurality of peer nodes including the own peer node and at least one other peer node constituting the P2P network; and a unit moving each of the divided files of distribution and arrangement between the plurality of peer nodes at a certain period of time.