An input circuit includes a pair of common-base circuits having respective transistors including respective bases to which differential signals transmitted through a transmission line are input and constant current sources connected to the emitters of the transistors, and a level shift circuit for inputting, to the emitters of the common-base circuits, differential signals with anti-phase relation to the differential signals input to the bases of the common-base circuits. This input circuit has lower power consumption and can be used to match impedance.