The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. A method performed by a terminal in a mobile communication system is provided according to one embodiment of the present disclosure. The method comprises the steps of: transmitting a first message, comprising network function information of the terminal, to a mobility management entity associated with a first network; if the network function information instructs support for a second network, receiving a second message comprising connection reactivation request information from the mobility management entity; releasing the connection with respect to the first network in response to the second message; transmitting a third message, for reestablishing connection to the first network, to the mobility management entity on the basis of the connection reactivation request information. The third message comprises an identifier of a first session for the second network corresponding to the connection with respect to the first network allocated by the terminal.