A transmitter apparatus wherein a simple structure is used to successfully suppress the degradation of error rate performance that otherwise would be caused by fading or the like. There are included encoding parts that encode transport data; a mapping part that performs such a mapping that encoded data sequentially formed by the encoding parts are not successively included in the same symbol, thereby forming data symbols; and a symbol interleaver that interleaves the data symbols. In this way, a low computational complexity can be used to perform an interleaving process equivalent to a bit interleaving process to effectively improve the reception quality at a receiving end.