A heterogeneous network system performs a vertical handover based on media independent handover (MIH) in different networks in which a WiMAX (Wireless Broadband Internet) network (or a WiBro (Wireless Broadband Internet)) and a WLAN (Wireless LAN) network are coexisted. The heterogeneous network system cyclically acquires neighboring network information in advance through a media independent handover server, and performs new address (NCoA) generation at a handover preliminary time. And then DAD (Duplicate Address Detection) and BU (Binding Update) are performed. Accordingly, the vertical handover between different networks can be performed to receive packets from a switched network while a handover delay time is minimized.