A method for transmitting a signal in broadcasting and communication systems is provided. The method includes dividing source data into two or more streams and respectively coding the two or more streams through coders, selecting two or more symbols from among coded codeword symbols, mapping the selected two or more symbols to one signal constellation for modulation, and transmitting a modulated signal, in which the codeword symbols include one or more non-binary codewords, and a product of orders of finite fields on which the codeword symbols are defined is equal to an order of the signal constellation.