Abstract: A calibration apparatus and method for use in a transmitting end of a multi-antenna system. The apparatus comprises at least two antennas, at least two transmitters for transmitting a signal through one of the antennas and transmitting a reference signal for channel estimation of transmission and reception paths, at least two receivers for receiving a signal through one of the antennas and coupling and receiving a reference signal transmitted through one of the antennas except the antenna for receiving the signal, and a calibration section for estimating channels for transmission and reception paths of the transmitters and the receivers using reference signals received by the receivers and calibrating signals to be transmitted through the transmission paths using the estimated channels.