The present specification pertains to a method by which a terminal feeds back CSI information in a wireless communication system to which 3D beamforming is applied, the method comprising the steps of: receiving a pilot signal from a base station; setting either a first CSI transmission mode or a second CSI transmission mode; and feeding back CSI information on the basis of the set CSI transmission mode. Here, a period and offset of the CSI information to be fed back can be preset regardless of the CSI transmission mode.