Abstract: In a calibration apparatus in a communication system, a modulation unit calculates a reference signal by modulating a downlink signal, and a digital Intermediate Frequency (IF) unit converts the reference signal to an intermediate frequency signal. An up-converter converts the intermediate frequency signal to a Radio Frequency (RF) signal, and a down-converter generates a received signal for each of the paths from the RF signal to be transmitted through each path. A calibrator calculates a correction value for each path and a delay value by using the reference signal and the received signal for each path.