Disclosed are a method and an apparatus of interference alignment in a cellular network. The method of interference alignment in the cellular network includes: receiving, by a base station, an improper signal from a terminal; and decoding, by the base station, the improper signal based on an improper decoding vector, wherein the improper signal is a signal generated by only a modulation symbol corresponding to a real number value, the improper decoding vector is determined based on an improper precoding vector, and the improper precoding vector has only the real value and separates a real number space and an imaginary number space of a received signal.