A method for channel sensing in an unlicensed band and transmitting downlink signals in a wireless communication system is disclosed. The method is performed by a transmission node configured to transmit the downlink signal after the channel sensing. The method includes sensing a channel scheduled to transmit downlink signals on a secondary cell (S-Cell) in the unlicensed band, and if the channel scheduled to transmit the downlink signals is determined to be in an unoccupied state according to the channel sensing, transmitting the downlink signals through a secondary cell (S-Cell) transmission structure having a boundary of a transmission unit shifted by a specific time index from a boundary of a transmission unit of a primary cell (P-Cell) transmission structure. The specific time index may be selected from among a plurality of candidate time indexes.