With the progress of communication systems, a wide variety of wireless terminals has been introduced to consumers such as companies and individuals. A current mobile communication system has been affiliated with Third Generation Partnership Project (3GPP), for example, Long Term Evolution (LTE), LTE-Advanced (LTE-A), and the like. Such a mobile communication system is a high-speed and high-capacity communication system capable of transmitting and receiving various data, such as image data, wireless data, and the like, beyond providing voice services. Accordingly, it is required to develop a technology for transmitting a large amount of data at a high speed similar to that of a wired communication network. Meanwhile, various deployments for multiple cells or a small cell have been introduced. Accordingly, there is a need for a technology and a method for enabling carrier aggregation to be applied in various development scenarios. Particularly, there is a need for a technology for controlling power transmission when uplink transmission is performed in multiple cells.