According to one embodiment, the present invention relates to channel sensing in an unlicensed band in a wireless communication system, and a data transmission method based on the same, wherein the method is performed by a transmission node for transmitting data by performing the channel sensing and comprises the steps of: receiving a data transmission instruction from a control node; performing a channel sensing-related operation in at least one of channel sensing-related operation execution sections set prior to each of a plurality of transmission opportunity units allowed at the transmission node, according to the data transmission instruction; and transmitting data according to the data transmission instruction in the transmission opportunity unit corresponding to a specific channel sensing-related operation execution section, if it is determined that a channel for transmitting the data is in the unoccupied state in the specific channel sensing-related operation execution section, wherein a transmission priority is assigned to each of the plurality of transmission opportunity units, and the length of the channel sensing-related opportunity execution section set prior to each of the plurality of transmission opportunity units can be adjusted according to the transmission priority assigned to each transmission opportunity unit.