Provided is a method of sending multiple codewords in a wireless communication system using a plurality of transmitting antennas. The method includes the steps of encoding a plurality of parallel information bit streams to generate a plurality of parallel codewords; modulating the plurality of parallel codewords to generate a plurality of parallel modulated symbol streams; performing a DFT (Discrete Fourier Transform) on the modulated symbol streams to generate a plurality of frequency domain symbol streams; performing a pre-coding process on the plurality of frequency domain symbol streams; mapping the plurality of precoded frequency domain symbol streams to resource elements; performing an IFFT (Inverse Fast Fourier Transform) on the plurality of frequency domain symbol streams to generate SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols; performing shifting, at a predetermined time interval, on layers at which the plurality of parallel codewords, the plurality of parallel modulated symbol streams, or the plurality of frequency domain symbol streams; and transmitting the SC-FDMA symbol.