A MIMO transmitting apparatus, receiving apparatus, transmission signal formation method, and transmission signal separation method with improved transmission efficiency. In communication apparatus, a mapping unit maps code words into a transmission stream on a per code-block basis and changes, between when a transport block is initially transmitted and when the transport block is retransmitted, the combinations of the code blocks mapped in the same transmission zone. In the communication apparatus, an interference replica generation unit forms, based on the decoded data of successfully decoded code blocks, an interference replica signal corresponding to the successfully decoded code blocks, and a signal separation unit removes, from a plurality of reception streams received this time, the interference replica signal formed by the interference replica generation unit received before the last time reception streams was received and then separates the reception streams received this time into each stream.