The present disclosure relates to a communication technique for fusing, with an IoT technology, a 5G communication system for supporting a higher data transmission rate than a 4G system, and a system therefor. The present disclosure may be applied to intelligent services, such as smart homes, smart buildings, smart cities, smart cars or connected cars, health care, digital education, retail businesses, and security and safety related services, on the basis of 5G communication technologies and IoT-related technologies. The present invention, according to one embodiment, may provide a method for requesting a service by a terminal, the method comprising the steps of: receiving, from a first network core, information for instructing a second network priority traffic; on the basis of the information for instructing the second network priority traffic, searching for a cell of a second network; and, if a cell accessible to the second network exists, transmitting a service request to the second network.