The present invention provides a method used in a wireless access system supporting carrier aggregation (CA) for acquiring uplink synchronization from two or more geographically spaced cells, and a device for supporting the same. According to one embodiment of the present invention, a method for acquiring uplink synchronization in a wireless access system supporting CA can comprise the steps of: receiving, from a primacy cell (PCell), random access channel (RACH) information related to a first random access step for matching uplink synchronization in a secondary cell (SCell) to be added to CA; and performing the first random access step for matching uplink synchronization in the SCell on the basis of the RACH information.