A method includes the steps of calculating a transmission power difference between a first carrier and a second carrier, and determining whether or not the transmission power difference exceeds a threshold set up on the basis of a maximum transmission power difference allowable between the first carrier and the second carrier. When the transmission power difference exceeds the threshold set up on the basis of the maximum transmission power difference, the transmission power of the first carrier or the second carrier is controlled while maintaining the transmission power difference within the maximum transmission power difference and not complying with power control information corresponding to the first carrier or the second carrier.