A method for transmitting a HARQ ACK/NACK feedback by a terminal may comprise: a step of transmitting, to a base station, a HARQ ACK/NACK feedback for a first downlink data, on a code block group (CBG) basis; a step of receiving, from the base station, a control channel including a specific control information; and a step of transmitting a HARQ ACK/NACK feedback on a transport block (TB) basis on the basis of the specific control information, for a second downlink data scheduled and received by the control channel, even if a CBG based retransmission is set for the terminal.