The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for transmitting an uplink signal. A method for transmitting an uplink signal at a UE in a wireless communication system includes, when a virtual cell ID for a reference signal for demodulation of a physical uplink channel is provided, generating a sequence of the reference signal on the basis of the virtual cell ID, and transmitting the generated reference signal to an eNB. A group hopping pattern of the reference signal can be determined on the basis of the virtual cell ID.