An apparatus and a method for transmitting a signal in a wireless communication system are disclosed. A method for transmitting a signal by a Base Station (BS) in a wireless communication system includes estimating an uplink channel using a signal received from a Mobile Station (MS), determining a beam coefficient for each of sub-carriers constituting a predetermined frequency band based on the estimated uplink channel, forming a beam for the predetermined frequency band by multiplying each sub-carrier by the beam coefficient, and transmitting a signal using the formed beam.