A wireless communication system and device improve throughput in a propagation path environment where retransmission is repeated. In a transmission-side wireless communication device, transmission signal storage memories hold bit sequences related to two packet signals for which NACK has been returned, a helper packet generation unit operates the exclusive OR of bit sequences related to two or more of a predetermined number of packet signals held in the transmission signal storage memories, and a coding unit to a transmitting and receiving antenna transmits an auxiliary packet generated by coding a bit sequence of a helper packet that is a result of the exclusive OR operation when the number of packet signals for which NACK has been returned reaches the predetermined number.