A handover performing method and apparatus are provided to allow a terminal to effectively perform handover when it moves from a cell of a base station supporting a legacy system to a cell of a base station supporting an advanced system. The method for performing handover by a terminal, includes: acquiring information regarding a target base station through scanning; transmitting a ranging request message including indication information indicating direct handover to the target base station to the target base station; receiving a ranging response message including a handover procedure optimization flag from the target base station; and performing a network entry procedure toward the target base station according to the handover procedure optimization flag, wherein, in the network entry procedure, a key agreement procedure with the target base station is performed by using first authentication information which has been used in a connection with a serving base station.