A service providing system, comprising: a first service providing means for providing a first service by executing a first application program; and a second service providing means for providing a second service by executing a second application program, wherein the first service providing means includes: an ID information provision request receiving means for receiving, from a first user terminal, an ID information provision request including a common ID that is information common to the first service and the second service and that is information for identifying a user; and an individual ID transmitting means for transmitting, to the first user terminal having transmitted the ID information provision request, a first individual ID that is information associated with the common ID included in the ID information provision request and that is information for identifying a user in the first service, and wherein the second service providing means includes: an ID information receiving means for receiving, from the first user terminal, a service ID that is information for identifying the first service, the first individual ID, and the common ID; an ID information acquisition request receiving means for receiving, from a second user terminal, an ID information acquisition request including a second individual ID that is information for identifying a user in the second service; and an ID information transmitting means for transmitting, to the second user terminal having transmitted the ID information acquisition request, the service ID and the first individual ID that have been received with the common ID associated with the second individual ID included in the ID information acquisition request. a first service providing means for providing a first service by executing a first application program; and a second service providing means for providing a second service by executing a second application program, wherein the first service providing means includes: an ID information provision request receiving means for receiving, from a first user terminal, an ID information provision request including a common ID that is information common to the first service and the second service and that is information for identifying a user; and an individual ID transmitting means for transmitting, to the first user terminal having transmitted the ID information provision request, a first individual ID that is information associated with the common ID included in the ID information provision request and that is information for identifying a user in the first service, and an ID information provision request receiving means for receiving, from a first user terminal, an ID information provision request including a common ID that is information common to the first service and the second service and that is information for identifying a user; and an individual ID transmitting means for transmitting, to the first user terminal having transmitted the ID information provision request, a first individual ID that is information associated with the common ID included in the ID information provision request and that is information for identifying a user in the first service, and wherein the second service providing means includes: an ID information receiving means for receiving, from the first user terminal, a service ID that is information for identifying the first service, the first individual ID, and the common ID; an ID information acquisition request receiving means for receiving, from a second user terminal, an ID information acquisition request including a second individual ID that is information for identifying a user in the second service; and an ID information transmitting means for transmitting, to the second user terminal having transmitted the ID information acquisition request, the service ID and the first individual ID that have been received with the common ID associated with the second individual ID included in the ID information acquisition request. an ID information receiving means for receiving, from the first user terminal, a service ID that is information for identifying the first service, the first individual ID, and the common ID; an ID information acquisition request receiving means for receiving, from a second user terminal, an ID information acquisition request including a second individual ID that is information for identifying a user in the second service; and an ID information transmitting means for transmitting, to the second user terminal having transmitted the ID information acquisition request, the service ID and the first individual ID that have been received with the common ID associated with the second individual ID included in the ID information acquisition request.