The present invention provides user equipment that transmits an uplink signal in a multi-carrier supporting mobile communication system and a method therefor, and a base station device that transmits uplink transmission power information and a method therefor. In the user equipment according to the present invention, a receiving antenna receives uplink transmission power information on a particular uplink carrier from the base station via a plurality of downlink carriers. A processor determines the transmission power of a signal to be transmitted via the particular uplink carrier, based on the uplink transmission power information that has been received. A receiving antenna then transmits the signal via an uplink carrier at the transmission power determined by the processor.