Provided are a method for performing, by a terminal, transmission power control in a wireless communication system, and a terminal using the method. The method is characterized by independently calculating first transmission power for wide area network (WAN) transmission performed in a first carrier wave, and second transmission power for transmission according to a device-to-device (D2D) operation performed in a second carrier wave, and reducing the second transmission power if the sum of the first transmission power and the second transmission power is greater than the maximum supported power of the terminal.