A transmission circuit includes a first semiconductor device, a second semiconductor device, a first signal line, a second signal line, a third signal line, and a ground line. A differential signal is composed of a first signal and a second signal. The first signal line is configured to connect the first semiconductor device and the second semiconductor device and used to transmit the first signal. The second signal line is configured to connect the first semiconductor device and the second semiconductor device and used to transmit the second signal. The second signal line, the first signal line, the ground line, and the third signal line are disposed in this order. A distance between the first signal line and the ground line is larger than a distance between the first signal line and the second signal line.