A transmission circuit includes a first path that connects a first terminal for inputting or outputting signals, and one of a pair of second terminals for outputting or inputting the signals; a second path that connects the first terminal and another one of the pair of second terminals; a first circuit including a first capacitor that is serially inserted in the first path, which is configured to perform single-differential conversion on signals transmitted through the first path, to perform impedance matching, and to supply a bias voltage; a second circuit including a first inductor that is serially inserted in the second path, which is configured to perform single-differential conversion on signals transmitted through the second path, to perform impedance matching, and to supply a bias voltage; and a switch that is connected between the two terminals of the pair of second terminals.