A method for selecting a serving AMF of a network node in a wireless communication system includes receiving a registration request message of a user equipment (UE), the registration request message including a network slice selection assistance information (NSSAI) for a slice requested by the UE and priority information of the NSSAI; determining whether the NSSAI is valid for the UE; when the NSSAI is valid for the UE, searching a first AMF which is able to support the NSSAI based on the priority information; and when the first AMF is searched, selecting the first AMF as the serving AMF serving the UE and transmitting the registration request message to the first AMF.