To relax the asymmetry of signals driven by a differential transmission circuit on signal transmission lines to reduce the radiative noise due to a common-mode current.

The differential transmission circuit 100 has a Pch and Nch transistors P2, N5 for driving a pair of signal transmission lines VH, VL, a difference signal detector 41 for detecting a signal potential difference between both the signal transmission lines VH, VL, a current mirror circuit 42 for turning a current back to the output, say, a reference current proportional the difference between a constant current and a current proportional to the potential difference, and control transistors N3, N4 for taking an output current of the current mirror circuit 42 as a discharge current from the gate electrodes of the Pch and Nch transistors P2, N5.