A power control method and an apparatus for controlling power mode of a User Equipment (UE) operating on multiple frequencies are provided. The terminal includes a primary module for primary cell communication and a secondary module for secondary cell communication. The method includes receiving a secondary cell adding message for adding a secondary cell from a base station, checking data-related information on data communicated through at least one of the primary module and a secondary module, and determining a power mode of the secondary module based on the checking.