Apparatus and method for transmitting and apparatus and method for receiving of multiple antenna system

A transmitting apparatus/method and a receiving apparatus/method in a multi-antenna system are provided to select the number of data streams adaptively to instantaneous changes of a channel, thereby preventing insufficiency of ranks, thereby considerably improving the bit error performance of a quantizing preprocessor. A transmitting apparatus(110) in a multi-antenna system comprises the followings: plural quantizing codebooks(113) which respectively correspond to each of data streams, and are formed by quantizing channel information between a transmitting antenna and a receiving antenna; a modulator(111) for modulating at least one data stream on the basis of an index of a stream mode included in information fed back from a receiving apparatus(120); and a quantizing preprocessor(112) which preprocesses the modulated data stream on the basis of a codeword index, selected from the quantizing codebooks(113) of the data stream corresponding to the stream mode of the index and included in information fed back from the receiving apparatus(120), and transmits the preprocessed data stream to the receiving apparatus(120).