The present disclosure relates to a communication technique that combines, with IoT technology, 5G communication system for supporting a higher data transfer rate than a 4G system, and a system therefor. The present disclosure can be applied to intelligent services, such as smart homes, smart buildings, smart cities, smart cars or connected cars, health care, digital education, retail businesses, security and safety related services, etc. on the basis of 5G communication technologies and IoT related technologies. Disclosed, in the present invention, are a method and an apparatus for determining the size of a transport block in a communication or broadcasting system.