Apparatus and method for refreshing master session key in wireless communication system

PURPOSE: A device for updating a master session key in a wireless communication system is provided to update a MSK(Master Session Key) through a EMSK(Extended Master Session Key) without renewing EAP(Extensible Authentication Protocol) in the wireless communication system. CONSTITUTION: A terminal(141) determines EMSK_Hash if a first key exchange message is received from a base station(123,125). The terminal transmits a second key message to the base station. If the second key message is received, the base station transmits a context request message to a ASN-GW(Access Service Network GateWay)(121). If the context request message is received, the ASN-GW transmits an authentication request message to an authentication server(111). If the authentication request message is received, the authentication server determines MSK1.