This specification relates to a frequency coexistence method, and more particularly, a carrier aggregation method and apparatus applicable in a wireless communication system using a multiple antenna regardless of an intra-band or inter-band. The carrier aggregation method may include using one baseband including two information and two radio frequency (RF) chains for aggregation of two component carriers at first and second frequency bands for each antenna port, switching the one baseband to at least one RF chain corresponding to the component carrier characteristic of the two RF chains upon use of the first frequency band and transmitting a signal through the switched at least one RF chain.