Disclosed are a data communication method using time division dual (TDD) cells of different frequency bands and a device thereof. The method includes: a step of setting connection of a first serving cell and a second serving cell between a base station and a terminal; a step of checking if the frequency bands of the first and the second serving cell are different from each other and if the TDD UL/DL configurations of the first serving cell and the second serving cell are different from each other; a step of determining if simultaneous transmission/receiving is available for frequency band combination of the first serving cell and the second serving cell; a step of, if the simultaneous transmission/receiving is available according to the determination result, determining a point of time to receive feedback and a point of time to retransmit for data transmitted to the second serving cell in consideration of the UL/DL configuration of the second serving cell; and a step of, if the simultaneous transmission/receiving is not available according to the determination result, determining a point of time to receive feedback and a point of time to retransmit for the data transmitted to the second serving cell in consideration of the UL/DL configuration of the first serving cell.