A lower layer retransmission control unit performs the following processing. When transmitting a transmission packet, giving a sequence number indicating a transmission order to the transmission packet. Receiving, from a receiving device that receives the transmission packet as a reception packet, an ACK packet indicating the sequence number of the reception packet. Referring to the sequence number of the received ACK packet to determine whether or not the ACK packet is received in an order of the sequence number. Transmitting first to third transmission packets and, if receiving a first ACK packet and receiving a third ACK packet following the first ACK packet without receiving a second ACK packet, performing fast retransmission control processing. Specifically, determining whether or not to receive the second ACK packet before a fast retransmission determination period passes after a reception time of the third ACK packet. If failing to receive the second ACK packet within the fast retransmission determination period, retransmitting the second transmission packet.