A packet data transmitting method and mobile communication system using the same enables transmission of common ACK/NACK information from each sector of a base station to a user entity in softer handover. The method includes receiving via at least one of the plurality of sectors a data packet from the mobile terminal, the data packet being correspondingly received for each of the at least one of the plurality of sectors; combining the correspondingly received data packets, to obtain a signal having a highest signal-to-noise ratio; decoding the value obtained by the combining; determining a transmission status of the data packet according to the decoding; and transmitting to the mobile terminal a common ACK/NACK signal including one of a common ACK signal and a common NACK signal according to the determining, the common ACK/NACK signal being transmitted via each of the at least one sector.