In a case where the F-RTO algorithm is simply combined with the exponential backoff algorithm which is being suppressed, there is a problem in that once a spurious timeout occurs, the spurious timeout continuously occurs since then. In order to solve the above problem, according to the present invention, in a communication device for transmitting data segments and receiving acknowledgements in response to the data segments, respectively and sequentially, suppressing an application of a backoff algorithm for increasing a retransmission timeout period at the time of retransmitting a data segment, and controlling the retransmission timeout period to retransmit the data segment, the spurious timeout is determined based upon the acknowledgement received immediately after the retransmission of the data segment. In an event of determining the occurrence of the spurious timeout, the retransmission timeout is increased.