A method for performing hierarchical beamforming in a wireless access system and a device therefor are disclosed. Particularly, the method comprises: an initial step for allowing a base station to transmit a plurality of first beams, to which different steering vectors are applied, to a terminal through corresponding reference signals, and a repetition step for allowing the base station to transmit a plurality of second beams, to which different steering vectors are applied, to the terminal through corresponding reference signals by considering feedback information that contains an index of one or more beams received from the terminal, wherein the repetition step can be repeated up to a predetermined number of times.