Provided are a method and apparatus for uplink transmission in a multi-antenna system. A terminal transmits a plurality of first transmission symbols via a plurality of antennas using a first spatial processing performed on the first transmission symbols, and transmits a plurality of second transmission symbols via a plurality of antennas using a second spatial processing performed on the second transmission symbols. At least one column or at least one row of a first spatial processing matrix used in the first spatial processing is switched to form a second SFBC matrix used in the second spatial processing. According to the present invention, peak-to average power (PAPR)/cubic metric (CM) ratio can be kept at a low level, and imbalanced transmission power among antennas can be evened out.