A communication method in a mobile communication system that copies and transmits data, to which transmission sequence numbers have been attached, over a plurality of paths from a mobile station to a radio network controller via a plurality of base stations; where the radio network controller monitors the communication state of each path, determines to transmit the data over all of a plurality of paths, transmit the data over two or more specified paths, or transmit the data over only one specified path, based on the communication state of each path, and notifies the mobile station of the determined path/paths; and where the mobile station transmits said copied data over said notified path/paths.