The present disclosure provides methods for allocating a timing advance (TA) value, which is used in a wireless access system supporting carrier aggregation (CA), methods for adjusting a wireless frame transmission time using the TA value, and apparatuses for supporting same. The method for adjusting the transmission timing in the wireless access system supporting carrier aggregation, according to one embodiment of the present disclosure, comprises the following steps: receiving a physical downlink control channel (PDCCH) signal including a reservation bit (for example, a service cell indicator) for indicating at least one serving cell; receiving a media access control (MAC) message including the TA value on an uplink wireless frame; and transmitting an uplink signal by applying the TA value from a serving cell indicated by the reservation bit.