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 (11—1-11—4) that encode transport data; a mapping part (3304) that performs such a mapping that encoded data sequentially formed by the encoding parts (11—1-11—4) are not successively included in the same symbol, thereby forming data symbols; and a symbol interleaver (3301) 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.