The present invention relates to a method for transmitting data by a base station in a wireless communication system supporting carrier aggregation, comprising the steps of: confirming whether a condition for data transmission distribution is satisfied; if the condition is satisfied, determining respective radio link control (RLC) data to be allocated to the base station and another base station, and sequence numbers for the RLC data; and transmitting the RLC data allocated to the other base station and the sequence numbers. However, the present invention is not limited to the embodiment above and other embodiments are possible.