The present disclosure relates to a communication technique for converging IoT technology with a 5G communication system for supporting a higher data transmission rate beyond a 4G system, and a system therefor. The present disclosure may be applied to an intelligent service (for example, a smart home, a smart building, a smart city, a smart car or connected car, health care, digital education, retail business a security and safety-related service, etc.) on the basis of 5G communication technology and IoT-related technology. The present invention relates to a method and a device for processing a message in a cell group radio link failure situation.