The present invention relates to a radio access system, and more particularly, to a method for efficiently performing handover in circumstances in which two networks use different communication methods, and to an apparatus using the method. According to one embodiment of the present invention, a method for performing handover in a first type of cell by a terminal supporting an inter-radio access technology (interRAT) handover (HO) comprises the steps of: searching for cells of a second type that are operating in accordance with a communication type different from that of said first type of cell; receiving a minimal reception signal quality value and signal quality offset information from a second type of base station which is found in step 1; determining whether or not the said found second type of base station is available for service based on a signal quality measurement value, a power compensation value, and said minimal reception signal quality value and signal quality offset information of said found second type of base station; and performing handover to said second type of base station when the latter is determined to be available for service.