The present invention provides a presence information management system, a presence server device, a gateway device and a client device, which notify of presence information in realtime while restraining communications traffic. The presence server device managing presence information of a plurality of presentities, comprises a delegating unit sending delegating notification of presence information management function related to at least one of the plurality of presentities, to another device becoming a delegatee of the presence information management function. The gateway device comprises a managing unit managing presence information of a presentity, and a control unit performing control so that, when receiving the delegating notification of the presence information management function about at least one of the plurality of presentities from a presence server, the managing unit is executed with respect to the function-delegated presentity.