An exemplary embodiment provides a carrier aggregation apparatus including: a level assignment manager configured to perform management by classifying a license band allocated to a cognitive radio cell into a primary radio resource (PRR) level, and by classifying a shareable band obtained through a cognitive radio database or spectrum sensing into an auxiliary radio resource (ARR) level; a determiner configured to determine a quality of service (QoS) level of a communication service provided to the cognitive radio cell; and a service provider configured to allocate a frequency resource of the PRR level when the QoS level requires a first communication service, and to allocate a frequency resource of the ARR level when the QoS level requires a second communication service lower than the first communication service.