The present invention relates to a wireless communication system and, more particularly, to a method and a device therefor, the method comprising the steps of: receiving scheduling information relating to uplink data; and transmitting the uplink data through a time slot having a plurality of symbols by using the scheduling information, wherein: when a reference signal for beam-arrangement is not transmitted in the time slot, a transmission beam direction of the uplink data remains the same in the time slot; and when the reference signal for beam-arrangement is transmitted in the time slot, the transmission beam direction of the uplink data is changed according to a transmission beam direction of the reference signal for beam-arrangement, in a symbol at which the reference signal for the beam-arrangement is transmitted in the time slot.