An operation method of a repeater performing relaying between a base station and a first terminal in a communication system may comprise: receiving one or more signals from at least one of the base station and the first terminal; performing monitoring on the one or more signals in a time interval for which a transmission direction is not determined by the base station; and determining the transmission direction of the time interval based on a result of the monitoring, wherein the one or more signals include at least one of a first signal received from the base station or a second signal received from the first terminal.