Disclosed is a method and an apparatus for transmitting/receiving signals in an multiple input multiple output (MIMO) wireless communication system. The method and apparatus including beam forming of a reference signal while predetermined codes are mapped on a one-to-one basis to each of a plurality of beams available for the transmitter and thereafter transmitting the beam-formed reference signal to a receiver. Also, if information representing an optimum beam, which maximizes reception performance, is received from the receiver, beam forming of data signals is performed by means of a beam corresponding to the information on the optimum beam and the beam-formed data signals are transmitted to the receiver. Therefore, it is possible to apply a beam forming scheme having minimum operation complexity and maximizing reception performance.