Apparatuses and methods for transmitting and receiving in a multi-antenna system are provided. A receiver for reducing a quantization error of channel information feedback in a multi-antenna system includes a restore vector generator for selecting a codeword ck and d determining a real part wkreal and an imaginary part wkimag of a restore vector corresponding to the codeword; and a post-processor for performing post-processing by multiplying the real part wkreal of the restore vector by a first reception signal and multiplying the imaginary part wkimag of the restore vector by a second reception signal.