A differential signal transmission cable structure for transmitting differential signals having GHz frequency band in the present invention is provided with a differential signal transmission pair cable 30 connecting a driver circuit 23a and a receiver circuit 23b, for transmitting differential signals having GHz frequency band, and a power supply ground transmission pair cable 31 connecting ground and a first power supply 26a connected to the driver circuit and ground and a second power supply 26b connected to the receiver circuit. Further characteristic impedance of the differential signal transmission pair cable is matched to that of the driver circuit and the receiver circuit, thereby enabling TEM waves of differential signals having GHz frequency band transmission mode to be maintained when the differential signals are transmitted.