Provided are a method whereby a terminal transmits an acknowledgement/not-acknowledgement (ACK/NACK) with a primary cell and a secondary cell aggregated, and a device for supporting the method. The method comprises: receiving data by a downlink subframe of a secondary cell; and transmitting an ACK/NACK for the data by an uplink subframe of a primary cell, wherein: the time interval between the downlink subframe and the uplink subframe is determined by a first hybrid automatic repeat request (HARQ) timing or a second HARQ timing; the first HARQ timing is an HARQ timing which is applied when the primary cell is used alone; and the second HARQ timing is an HARQ timing which is additional to the first HARQ timing.