Disclosed are an apparatus and a method for detecting signals in a spatial multiplexing system. An embodiment of the invention provides a signal detection apparatus for a single receiver unit equipped with a plurality of antennas in a system having at least one transmitter unit configured to transmit data streams by spatial multiplexing, where the signal detection apparatus includes: a partial linear coefficient generator unit configured to generate a linear weighting matrix by using a preset algorithm on a channel matrix formed between the transmitter unit and the single receiver unit; a partial symbol remover unit configured to generate a first symbol vector by removing all transmittable symbols for each transmitting antenna from all received data streams; and a partial symbol detector unit configured to generate a transmission symbol candidate vector by using the linear weighting matrix and the first symbol vector.