Disclosed is a method of using relay that may continuously transmit data without time division based on superposition coding in a communication system. When transmission of a relay-supported user signal via a base station-relay link is performed, the method of using relay based on the superposition coding reuses a resource allocated to a direct-transmission user based on the superposition coding to perform the transmission. According to example embodiments, a separate resource for the base station-relay link may not be needed, and continuous relay transmission is possible without time division, thereby substantially increasing frequency efficiency and reducing a transmission delay caused by the use of the relay.