The present invention relates to a method and a device for managing carriers allocated to a terminal in a broadband wireless access system that supports multi-carrier. A method for managing carriers by a terminal in a broadband wireless access system supporting multi-carrier includes transmitting, to a base station, activation requests information for requesting the activation of at least one second carrier allocated from the base station through a first carrier according to the power state of the terminal, receiving, from the base station, a first message that includes activation indication information for indicating the activation of at least one target carrier of the at least one second carrier, and transmitting to the base station a second message which notifies the base station whether the at least one target carrier is ready per activation.