Methods of transmitting data using a plurality of hybrid automatic repeat request (HARQ) process channels sequentially is disclosed. One of the methods of transmitting data through a plurality of HARQ process channels including a first channel and a second channel includes adding offset to a retransmission data block if the first channel which will transmit the retransmission data block is prescheduled (S702) by another data block, the offset representing the difference in a transmission timing point between the second channel in which positive acknowledgement (ACK) signal has been received (S701) and the first channel; transmitting the retransmission data block through the second channel; and transmitting a data block corresponding to the second channel through the first channel.