A radiation noise suppression circuit for a differential transmission line includes a differential transmission line which has plus line signal wiring to which a plus line signal of a differential signal is applied, and minus line signal wiring to which a minus line signal of the differential signal is applied, and connects a differential driver and a differential receiver. Plus line signal GND wiring and minus line signal GND wiring which are connected between the differential driver and the differential receiver are wired along the differential transmission line. A distance between the plus line signal wiring and the plus line signal GND wiring is substantially equal to a distance between the minus line signal wiring and the minus line signal GND wiring.