A method for reporting a channel state on a downlink channel transmitted through M antenna ports that are 2-dimensionally arranged according to an embodiment of the present invention may be performed by a terminal and include a step of receiving a channel state information-reference signal (CSI-RS) setting for N virtual antenna ports that are formed by applying beam-forming to a group of vertical antennas of the 2-dimensionally arranged M antenna ports, and a step of calculating channel state information on the downlink channel by using the received CSI-RS setting to report the channel state information to a serving cell, wherein the reported channel state information may include information on a rotational transformation related to a first code word of a codebook related to a combination of Q unit vectors that are orthogonal in an N dimension space.