A transfer device for a system in which transmission sources connect to the transfer device, transmission destinations connect to another transfer device, the transfer devices (100, 200) connect to each other via a network, and the transmission sources and transmission destinations perform data communication via the transfer devices (100, 200), the transfer device comprising: a transfer unit configured to establish connections with, and receive TCP, Transport Control Protocol, packets from, the transmission sources; a band allocation unit configured to: calculate a first bit rate that is to be allocated to a plurality of groups each consisting of transmission sources and transmission destinations, according to the equation: Total X = min b, R X + Bnow × T X + R X / TotalSize wherein Total is the first bit rate to be allocated to each group, b is a minimum bit rate value set by a user, R is a total size value of UDP, User Datagram Protocol, packets retransmitted to the other transfer device per unit time, min( b, R) is a function that selects the smaller value of b and R, Bnow is a remaining bit rate value obtained by subtracting a total value of minimum bit rates that are to be respectively allocated to the plurality of groups from a maximum bit rate value set by the user, T is a total size of TCP packets per unit time, and TotalSize is a total value of data amount per unit time in data communication between the plurality of groups, and allocate the first bit rate to each of the groups; and a transfer control unit configured to: establish a connection with the other transfer device, within the first bit rate allocated to each group by the band allocation unit, convert TCP packets received from the transmission sources of the group to UDP packets by encapsulating the received TCP packets with UDP headers, transmit the UDP packets to the other transfer device for transfer to the transmission destinations of the group, and retransmit UDP packets to the other transfer device in response to retransmission requests received from the other transfer device. a transfer unit configured to establish connections with, and receive TCP, Transport Control Protocol, packets from, the transmission sources; a band allocation unit configured to: calculate a first bit rate that is to be allocated to a plurality of groups each consisting of transmission sources and transmission destinations, according to the equation: Total X = min b, R X + Bnow × T X + R X / TotalSize wherein Total is the first bit rate to be allocated to each group, b is a minimum bit rate value set by a user, R is a total size value of UDP, User Datagram Protocol, packets retransmitted to the other transfer device per unit time, min( b, R) is a function that selects the smaller value of b and R, Bnow is a remaining bit rate value obtained by subtracting a total value of minimum bit rates that are to be respectively allocated to the plurality of groups from a maximum bit rate value set by the user, T is a total size of TCP packets per unit time, and TotalSize is a total value of data amount per unit time in data communication between the plurality of groups, and allocate the first bit rate to each of the groups; and calculate a first bit rate that is to be allocated to a plurality of groups each consisting of transmission sources and transmission destinations, according to the equation: Total X = min b, R X + Bnow × T X + R X / TotalSize wherein Total is the first bit rate to be allocated to each group, b is a minimum bit rate value set by a user, R is a total size value of UDP, User Datagram Protocol, packets retransmitted to the other transfer device per unit time, min( b, R) is a function that selects the smaller value of b and R, Bnow is a remaining bit rate value obtained by subtracting a total value of minimum bit rates that are to be respectively allocated to the plurality of groups from a maximum bit rate value set by the user, T is a total size of TCP packets per unit time, and TotalSize is a total value of data amount per unit time in data communication between the plurality of groups, and allocate the first bit rate to each of the groups; and a transfer control unit configured to: establish a connection with the other transfer device, within the first bit rate allocated to each group by the band allocation unit, convert TCP packets received from the transmission sources of the group to UDP packets by encapsulating the received TCP packets with UDP headers, transmit the UDP packets to the other transfer device for transfer to the transmission destinations of the group, and retransmit UDP packets to the other transfer device in response to retransmission requests received from the other transfer device. establish a connection with the other transfer device, within the first bit rate allocated to each group by the band allocation unit, convert TCP packets received from the transmission sources of the group to UDP packets by encapsulating the received TCP packets with UDP headers, transmit the UDP packets to the other transfer device for transfer to the transmission destinations of the group, and retransmit UDP packets to the other transfer device in response to retransmission requests received from the other transfer device.