One embodiment of the present specification suggests a method and an apparatus for supporting a plurality of carriers in a single UE. Each carrier can support V2X communication of various standards. The UE can perform an improved backoff operation for at least one carrier. The backoff operation applied to any one of the carriers can be performed on the basis of the operation of another carrier. For example, the backoff operation can be performed on the basis of whether or not a signal is received by the other carrier. The backoff operation based on the present specification can solve a technical problem which arises when different operations are performed in the plurality of carriers.