Embodiments of the present invention relate to a method and terminal device for controlling uplink transmission power. According to one embodiment, in which a terminal that communicates with cells of each timing alignment (TA) group controls uplink transmission power in the event a plurality of TA groups including one or more cells exists in a wireless communication system, a method includes: determining the uplink transmission power for at least one channel in the event at least two channels from among a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH) including a plurality of pieces of uplink control information (UCI), a PUSCH including no UCI, a physical random access channel (PRACH), and a sounding reference signal (SRS) are simultaneously transmitted in the same subframe in each specific cell of the plurality of TA groups. The uplink transmission power is determined in consideration of a TA group index.