A communication terminal used in a communication system which sets a communication session between a plurality of terminals through a network to perform data transmission and reception includes a first transmission bandwidth control unit which performs transmission bandwidth control independently of a state of the network, a second transmission bandwidth control unit which performs transmission bandwidth control depending on a state of the network, and a bandwidth estimating unit which determines a transmission bandwidth when bandwidth control by the second transmission bandwidth control unit is started. When transmission is started, bandwidth control by the first transmission bandwidth control unit is performed, and when a transmission bandwidth is determined by the bandwidth estimating unit on the basis of a response packet to a transmission packet based on the bandwidth control, the bandwidth control by the second transmission bandwidth control unit is performed.