A transmitter, a receiver and signal processing methods are provided. The transmitter includes: an encoder configured to perform encoding on an information word based on a parity check matrix to generate a codeword including a plurality of non-binary symbols; an interleaver configured to interleave the codeword; and as modulator configured to modulate the interleaved codeword to generate a plurality of modulation symbols. The interleaver is configured to interleave the codeword such that the modulator maps a predetermined non-binary symbol from among the plurality of non-binary symbols constituting the codeword to a predetermined position in a modulation symbol among the plurality of modulation symbols.