The present invention relates to a wireless communication system. More particularly, the present invention relates to a method for transmitting uplink control information, and to an apparatus for the method, wherein the method comprises the steps of: generating a plurality of HRAQ-ACKs; selecting, from among a plurality of resource indices, one first resource index, and two second resource indices, each corresponding to the plurality of HARQ-ACKs; transmitting, through a first antenna port, a first modulation symbol corresponding to the plurality of HARQ-ACKs and a first reference signal for demodulating the first modulation symbol; and transmitting, through a second antenna port, a second modulation symbol corresponding to the plurality of HARQ-ACKs and a second reference signal for demodulating the second modulation symbol. Both a transmission resource for the first modulation symbol and a transmission resource for the first reference signal are given using said one first resource index. A transmission resource for the second modulation symbol is given using one of said two second resource indices, and a transmission resource for the second reference signal is given using the other of said two second resource indices.