Disclosed is a method of selecting a transmission antenna in a radio communication system. The present invention includes the steps of transmitting data through a sequentially selected antenna and if error occurs in the transmitted data, retransmitting corresponding erroneous data. Therefore, present invention presumes what channel state of antennas is better based on the response signal (ACK or NACK) of the reception party and then transmits data through the presumed antenna, thereby enabling to improve transmission performance more.