Provided is a communication method of a terminal in a multi-carrier system using a plurality of component carriers. The method includes: receiving a reconfiguration message indicating whether downlink control information (DCI) includes a carrier indication field (CIF); receiving a plurality of DCIs indicating a resource used to transmit a reconfiguration complete message in response to the reconfiguration message; and transmitting the reconfiguration complete message on the basis of resource allocation information included in DCI which is successfully decoded among the plurality of DCIs, wherein the plurality of DCIs include first DCI used before the CIF of the DCI is reconfigured by the reconfiguration message and second DCI used after the CIF of the DCI is reconfigured by the reconfiguration message.