Provided are a method for performing a hybrid automatic repeat request (HARQ) of a frequency division duplex (FDD) cell in a wireless communication system and a wireless device using the same. The wireless device receives an uplink-downlink (UL-DL) configuration for an uplink (UL) carrier of the FDD cell, and performs the HARQ in a DL carrier of the FDD cell on the basis of HARQ timing determined according to the UL-DL configuration.