The present disclosure relates to a communication technique for combining, with an IoT technology, a 5G communication system for supporting a data transmission rate higher than that of a 4G system, and to a system therefor. The present disclosure may be applied to intelligent services (e.g., a smart home, a smart building, a smart city, a smart car or connected car, healthcare, digital education, retail business, security and safety-related service, etc.), based on a 5G communication technology and an IoT-related technology. A method for a user equipment in a first communication system according to the present invention comprises a user equipment in an inactive state: transmits a paging area update request message; checks whether a timer associated with a paging area update has expired; and transitions into an idle state if a response message for the paging area update request message has not been received until the timer expired.