A bridge node converts a MAC frame addressed to a station node into a RPR MAC frame and thus transmits it, and encapsulates a MAC frame addressed a station being located the outside of a ring and connected to other bridge node into the RPR MAC frame, and transmits it. The bridge node thereby receives a RPR MAC frame into which the MAC frame is encapsulated, and the station node receives the RPR MAC frame that the MAC frame is not encapsulated.