A method of performing channel access on an unlicensed band by a user equipment in a wireless communication system, includes sensing a carrier of an unlicensed band for receiving a downlink signal; and receiving the downlink signal when power detected by sensing the carrier is less than an energy detection threshold that is configured by a base station, wherein the energy detection threshold is configured to be equal to or less than a maximum energy detection threshold determined by the base station, and wherein when a different radio access technology (RAT) sharing the carrier is able to exist, the maximum energy detection threshold is determined adaptively to a bandwidth of the carrier using a decibel value of a ratio between a reference bandwidth and the bandwidth of the carrier.