The present invention relates to a method for transmitting response information on downlink data through multiple information blocks to be bundled in a wireless system in a time division duplex (TDD) mode. The method for transmitting response information according to the present invention comprises the following steps: coding response information on the downlink data; scrambling the coded response information; and transmitting the scrambled response information to a base station, wherein, if a portion of the bits of the coded response information are information bits that indicate ACK/NACK on the downlink data, the scrambling step involves scrambling the coded response information using a specific scrambling sequence, and the specific scrambling sequence includes information on the number of information blocks to be bundled.