PROBLEM TO BE SOLVED: To acquire synchronization at high speed even for an device having low throughput, and to improve confidentiality in speech communication. SOLUTION: When a control means 240 identifies a called terminal device, to which an incoming call request is made from a telephone network 400, the control means 240 selects an idle spread spectrum modulating/demodulating means out of a plurality of spread spectrum modulating/demodulating means 210, and sets a spreading code for synchronization to the selected spread spectrum modulating/demodulating means. The selected spread spectrum modulating/ demodulating means performs modulation by the spreading code for synchronization. A transmission/reception means transmits the modulated signal to the called terminal device by the spreading code for synchronization. When the synchronization is acquired with the called terminal device, the control means 240 sets the spreading code for communication which is different from the spreading code for synchronization and is intrinsic to the called terminal device to the selected spectrum modulating/demodulating means, and make communication with the called terminal device.