A data processing method and a data re-transmission method in a broadband wireless access system are disclosed. A transmitting side generates a coded block set including coded blocks of a predetermined number and the coded blocks are transmitted to first and second base stations. The transmitting side sets a timer after transmitting a last coded block of the coded blocks. The coded blocks received by the second base station are transmitted to the first base station, and the transmitting side receives a control signal indicating whether there is a transmission error from the first base station.