A communication method for a channel access in a wireless communication system and an apparatus therefor are provided. The communication method includes an evolved NodeB (eNB) that transmits data to a user equipment (UE) through a licensed band, and determines whether an unlicensed band channel is in an idle state during a first channel sensing duration. If the unlicensed band channel is in the idle state, the eNB transmits data to the UE through an unlicensed band during a first channel occupying duration, a second channel sensing duration, and a second channel occupying duration. In the method, a sum of the first channel occupying duration, the second channel sensing duration, and the second channel occupying duration is equal to or less than a certain time.