An apparatus for transmitting data in a base station of a wireless communication system that transmits data depending on channel status information fed back from terminals and uses a plurality of antennas. Based on the channel status information, a scheduler determines a terminal to which the base station will transmit data, determines antennas via which the base station will transmit data among the plurality of antennas, and determines a space pre-coding method. A multiplexer multiplexes transmission data into a plurality of data streams according to the number of the determined antennas. A modulation and coding unit performs modulation and coding on each of the data streams. A pre-coding controller outputs a matrix select signal for selecting one of a plurality of space pre-coding matrixes according to the space pre-coding method. A space pre-coder spatial-codes each of the coded streams with the matrix selected based on the matrix select signal. An OFDM modulator performs OFDM modulation on each of the spatial-coded streams. An RF unit transmits each of the OFDM-modulated streams via an associated antenna.