Apparatus and method for supporting access to private mobile communication network and carrier mobile communication network

An access and mobility management function (AMF) of a first network which registers a user equipment (UE) at a second network via the first network, the AMF comprising:

• a transceiver;
• and
• a controller combined with the transceiver and configured to receive, from the UE, a registration request message comprising at least one of first network identification (ID) information, ID information of the UE in the first network, second network ID information, and ID information of the UE in the second network, select an authentication server function (AUSF) of the first network which is configured to perform a first authentication procedure of service subscription authentication for the UE in the first network, perform the first authentication procedure with the AUSF of the first network and unified data management (UDM) of the first network, determine, based on a result of the first authentication procedure, whether to perform a second authentication procedure of service subscription authentication for the UE in the second network, perform, based on a result of the determining, the second authentication procedure with an AUSF of the second network and UDM of the second network, and transmit, to the UE, a registration acceptance message comprising information of at least one of the result of the first authentication procedure and a result of the second authentication procedure.