A disclosure of the present specification provides a method for determining uplink transmission power by a wireless device. The transmission power determination method may comprise the steps of: determining whether transmission of uplink data uses 64 quadrature amplitude modulation (QAM) or not; determining whether transmission of the uplink data corresponds to multi-clustered transmission or not; determining whether transmission of the uplink data is to be performed through a single carrier or is to be performed through a plurality of carriers according to carrier aggregation; and determining a maximum power reduction (MPR) value, which is to be applied to transmission of the uplink data, according to the determination results. Here, when transmission of the uplink data uses the 64 QAM, corresponds to the multi-clustered transmission, and is performed through the single carrier, a first MPR value may be determined; and, when transmission of the uplink data uses the 64 QAM, corresponds to the multi-clustered transmission, and is performed through the plurality of carriers, a second MPR value may be determined.