The present invention relates to a wireless communication system. Particularly, the present invention provides a method for enabling a user equipment (UE) to retransmit uplink data on the basis of a signal received through a physical hybrid ARQ indicator channel (PHICH) in a wireless communication system and a device for the same, and the method for retransmitting uplink data comprises the steps of: receiving, from a base station, an indication on whether or not to detect the PHICH; retransmitting the uplink data on the basis of a PHICH detection result if the received indication is to detect the PHICH; and retransmitting the uplink data on the basis of an uplink grant received from the base station if the received indication is not to detect the PHICH.