A method of feeding back channel information by a receiver in a communication system beam forming is provided. The method includes determining an optimum reception beam using intensities of reference signals received through transmission beams of a base station for a first period through a first path for mapping analog beams of an input signal, and determining an optimum transmission beam of the transmission beams using intensities of reference signals received through the optimum reception beam for a second period through a second path for mapping analog beams of the input signal, and transmitting channel information measured by using a reference signal received through the optimum transmission beam and the optical reception beam to a transmitter.