A method for a base station for transmitting a downlink signal in a wireless communication system according to one embodiment of the present invention comprises the steps of: modulating, of a codeword of a first terminal, a first part by means of a first modulation and coding scheme (MCS) and a second part by means of a second MCS; and transmitting the modulated codeword to the first terminal, wherein the second part of the codeword is transmitted along with a signal of a second terminal from the same resource on the basis of the non-orthogonal multiple access (NOMA) method, and the second MCS for the second part, transmitted on the basis of the NOMA method, has a lower modulation order than the first MCS for the first part.