The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and an apparatus for transmitting ACK and NACK with a terminal set in a state of ACK/NACK repetition mode, and the method comprises the steps of: receiving first data through a first subframe; receiving second data through a second subframe; and transmitting an ACK/NACK signal for the second data, wherein the repetition frequency of the ACK/NACK signal for the second data is reduced if a difference between the first subframe and the second subframe is smaller than a reference value.