A apparatus and method for transmitting channel state information is disclosed. If an LTE-A system transmits a reference signal per subframe to support eight transmitting antennas, a problem occurs in that overhead is great. In order to solve this problem, a reference signal for channel measurement is transmitted per subband at different periods, or a user equipment scheduled for channel measurement uses a demodulation reference signal. The user equipment can notify a base station of channel measurement result using the demodulation reference signal in accordance with implicit or explicit signaling from the base station.