The present invention relates to a method in which a receiver transmits control information in a wireless communication system. The method comprises a step of receiving a plurality of data units from a transmitter, a step of determining acknowledgement/negative-acknowledgement (ACK/NACK) states for each of the data units; and a step of transmitting, to the transmitter, the ACK/NACK states in multiple ACK/NACK states or in a single ACK/NACK state in accordance with a predetermined condition.