A serving cell change method and apparatus is provided for efficiently performing the serving cell change in a mobile communication system. The UE receives a cell change control information including an activation time from a serving cell, when a downlink channel status of the serving cell is inferior to a downlink channel status of a target cell, reports a measurement result to the serving cell while performing data communication with the serving cell, monitors receipt of a cell change indicator transmitted by the target cell before the expiration of the activation time while performing the data communication with the serving cell, and when the cell change indicator is received, communicates data with the target cell by sending an acknowledgement in response to the cell change indicator and switching to the target cell.