The present invention is to provide a node device, a shared information update processing program, a shared information update means, and an information sharing system, which can quickly and assuredly update the shared information in each of the node devices without applying an excessive load to a specific apparatus such as a server.According to the present invention, there is provided a plurality of node devices mutually connectable through a network, each of the node devices saving shared information, used in common with the nodes, and in a case where each of the node devices transmits predetermined data to the node device, being a connection counterpart, the node device describing version information indicative of a version of the shared information, saved by the own node device, including: a data receiving means; a version judgment means; and a shared information update means.