1. A method for detecting a signal from a receiving device in a communication system comprising a multi-output multi-input antenna, comprising: estimating a channel matrix of a signal received from a plurality of receiving antennas; generating at least one channel matrix group by aligning the channel matrix, and generating at least one transmitting signal group by aligning a transmitting signal to be estimated to correspond thereto; determining a first candidate vector in consideration of all constellation points for a first layer of the at least one transmitting signal group; determining a second candidate vector in consideration of all constellation points for a second layer of the at least one transmitting signal group; generating a final candidate vector comprising the first candidate vector and the second candidate vector; and calculating a soft output using the final candidate vector.