1. A method for feeding back channel state information (CSI) by a user equipment (UE) in a wireless communication system supporting a 3-dimensional multiple-input multiple-output (3D-MIMO) antenna, the method comprising:receiving, through radio resource control (RRC) signaling, information about N beams (where N is a natural number) precoded for specific antennas among multiple antennas constituting the 3D-MIMO antenna and information about a number M of interference beams (where M is a natural number, M?N?1);
selecting a specific beam for generating the CSI from among the N beams;
determining M beams among the remaining beams in descending order of the difference from the index of the specific beam; and
generating the CSI for the specific beam using the interference determined based on the M beams.