Disclosed is a data transmission/reception apparatus and method for minimizing decoding errors during high-speed packet transmission in a CDMA mobile communication system. When retransmitting data in the Hybrid Automatic Repeat Request (“H-ARQ”) technique, the data transmission/reception apparatus and method performs symbol mapping on coded bits to be retransmitted by allocating different reliabilities to the coded bits according to the number of retransmissions, thus resulting in an improvement of system performance.