The present disclosure relates to a communication technique and system for integrating a 5G communication system for supporting a higher data rate after a 4G system with IoT technology. Based on 5G communication technology and IoT related technology, this disclosure may be applied to an intelligent service (e.g., smart home, smart building, smart city, smart car or connected car, health care, digital education, retail, security and safety related service). Embodiments relate to a method and apparatus for performing an access in an RRC inactive mode in a next generation mobile communication system.