A method for performing a power scaling is discussed. The method performed by a user equipment (UE) includes determining, by the UE configured with dual connectivity to a master cell group (MCG) and a secondary cell group (SCG), a first power for a first transmission in a first subframe toward the MCG, determining a second power for a second transmission toward the SCG, and scaling down the second power for the second transmission toward the SCG if a total power related to the MCG and the SCG exceeds a maximum power, wherein the scaling down is performed if the first transmission toward the MCG in the first subframe is overlapped with the second transmission toward the SCG.