Abstract: An apparatus is provided for detecting a signal in a communication system using a Multiple Input Multiple Output (MIMO) scheme. The signal detection apparatus includes a detector for generating second matrixes by extending a first matrix composed of channel response vectors, generating specific matrixes by decomposing the second matrixes, generating a lattice point of vectors constituting the second matrixes, estimating a signal using the generated specific matrixes and lattice point, and detecting the estimated signal as a received signal if the estimated signal has a value within a predetermined allowable range.