A drive circuit includes a bias current supply circuit for supplying a bias current to a light-emitting device for transmitting an optical signal, the light-emitting device included in a light-emitting circuit; and a modulation current supply circuit for supplying a modulation current of a magnitude according to a logical value of data to be transmitted, to the light-emitting device. The modulation current supply circuit includes a differential drive circuit for switching whether to supply a current to the light-emitting device, according to the logical value of the data; and a termination resistor connected between differential outputs of the differential drive circuit. The differential drive circuit and the light-emitting circuit are DC-coupled to each other, and power supply of the current supplied to the light-emitting device by the differential drive circuit is supplied from the light-emitting circuit.