A method by which a terminal demodulates a signal in a wireless access system according to one embodiment of the present invention comprises the steps of: receiving a modulation signal having a modulation order of 2m (m is a natural number); determining a first demodulation constellation arrangement corresponding to a kth (k is an even number among natural numbers of m or less) bit among m numbers of bits; determining a second demodulation constellation arrangement corresponding to an nth (n is an odd number among natural numbers of m or less) bit among the m numbers of bits; and demodulating the received modulation signal by using the first and second demodulation constellation arrangements, wherein the first constellation arrangement can have a pattern in which a square matrix having a size of 2(m/2+1)−(k/2) is repeated.