The present disclosure relates to communication methods and systems for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. Disclosed are reliable transmission methods for ultra-reliable low-latency communication (URLLC) in 5G next-generation core networks, which provide methods of redundant transmission through a plurality of transmission paths in order to perform transmission between radio access networks (RANs) through ultra-reliable transmission in the core network. The disclosure also provides simple multiple path transmission and multiple path transmission using an intermedia user plane function (I-UPF) according to the deployment environment of a network router.