Method for reporting csi in wireless communication system and device for same

Disclosed in the present invention is a method for reporting, by a terminal, channel status information (CSI) to a base station in a wireless access system. The CSI reporting method is characterized by including the steps of: transmitting, to a base station, first CSI including a rank indicator in a first period unit; transmitting, to the base station, second CSI including a vertical precoding matrix index in a second period unit within the first period; and transmitting, to the base station, third CSI including horizontal precoding matrix index in a third period unit within the second period.