A data transmitting/receiving method and apparatus for allocating optimal sub-bands and transmission power levels and transmitting data in a ultra wide band (UWB) communication system. The method includes receiving data through sub-bands of each band group; determining performance ranks of the sub-bands based on error rates and differences of transmitting and receiving power levels of the received data; selecting a predetermined number of sub-bands according to the performance ranks of the sub-bands; generating power level adjustment information based on measured power levels of data of the selected sub-bands; and receiving data according to the selected sub-bands and the power levels.