To provide an effective MIMO signal separating process, in the MIMO (Multiple-Input Multiple-Output) transmission, and also obtain a sufficient improvement in characteristics even in the re-transmission synthesis even when correlation between the transmitting antennas and between the receiving antennas is high.

The communication system comprises a channel estimating means 23 for obtaining a channel estimation value hij (j=1, 2) between the transmitting antenna and the receiving antenna 21-i from the receiving signal received with each receiving antenna 21-i (i=1, 2), a memory 24 for holding a receiving signal yi and a channel estimation value hij obtained with the channel estimating means 23, and a signal reproducing/separating means 25 for reproducing and separating the signal transmitted from each transmitting antenna with the transmitting apparatus on the basis of the retransmitting signal retransmitted from the transmitting apparatus, the channel estimation value obtained with the channel estimating means 23 for the relevant retransmitting signal, and the receiving signal yi and channel estimation value hij stored in the memory 24.